Method and apparatus for cracking nuts

The nut cracking apparatus includes a conveyor comprised of a plurality of parallel slats connected to endless chains for intermittent movement from a hopper to a nut gripping and cracking apparatus. Each slat is provided with a row of openings extending therethrough for receiving nuts from the hopper and an underlying support is provided to retain the nuts in the openings until each slat is moved in sequence to a plurality of cracking apparatus. Each nut is located between an upper and lower nut gripping block each of which has a recess therein with a slot in the bottom thereof. The lower nut gripping block is spring biased on a fixed blade to normally have the blade retracted out of the recess. The upper nut gripping block is spring biased on an opposed blade which in turn is connected to the piston of an hydraulically operated piston and cylinder device. The upper nut gripping block is normally biased so that the blade is withdrawn from the recess. Upon lowering of the upper blade toward the lower blade a nut is gripped between the upper and lower blocks and continued downward movement of the blade will cause the upper and lower blades to penetrate into the recesses to cut the shell of the nut into two pieces without damaging the kernel of the nut. A blade position sensing device is provided for limiting the travel of the blade and upon cutting the shell into two pieces, the upper blade is retracted and the upper and lower nut gripping blocks are spring biased back to their normal position. Upon the next stepwise movement of the belt, the slat is moved to a position whereby the shell pieces will drop from the openings in the slat to a container.

BACKGROUND OF THE INVENTION 
The present invention is directed to a method and apparatus for cracking 
nuts of the type having very hard shells such as macadamia nuts or 
walnuts. In the past a great deal of skill was required to crack nuts 
having a kernel such as macadamia nuts in a highly efficient manner 
without damaging the kernels. 
U.S. Pat. No. 4,135,442 discloses a nut cracking machine wherein a nut is 
held between two dish-shaped dies. Means are provided for applying a 
sudden impact to one of the dies thereby causing the die to move a limited 
distance to crack the nut. When the nut is cracked or crushed in this 
manner, the shell scatters and the kernel of the nut is in danager of 
being damaged. The cracking machine makes it impossible to divide the 
shell into two pieces without damaging the kernel. 
U.S. Pat. No. 4,200,042 discloses a nut cracker having first and second 
levers which are pivotally connected together at one end and have opposed 
portions provided with one or more cross-grooves for receiving nuts to be 
cracked. These grooves have a varying depth from one end to the other and 
also have a varying width thus accommodating a wide range of nut sizes. 
The grooves also have transverse ribs to hold the nuts in place while 
being cracked and in a preferred structure, the grooves are defined by 
straight wall segments meeting in angular relation. One of the levers may 
comprise a base portion and the other lever may include a handle for 
applying leverage. When the nuts are placed in these grooves and the 
levers brought together, the nuts are crushed without cutting the shell so 
that there is a distinct possibility that the kernels of the nuts will be 
damaged because of the scattering of the shell. 
In the past the cracking of nuts was generally a laborious and time 
consuming operation even when using the apparatus disclosed in the two 
above-identified patents. The nuts were usually cracked one-by-one and 
some element of manual labor was generally required. 
SUMMARY OF THE INVENTION 
The present invention provides a new and improved apparatus for 
continuously cracking nuts by dividing the shells into two pieces without 
scattering of the shells and without damaging the kernels of the nuts. 
The present invention provides a new and improved apparatus for cracking 
nuts wherein conveying means are provided for intermittently conveying a 
plurality of nuts simultaneously to a cracking station. The conveying 
means includes a plurality of transverse slats connected between two 
conveyor chains with each slat having a plurality of cylindrical openings 
therethrough each of which is adapted to receive a nut for movement along 
a supporting surface. The cracking station includes a plurality of pairs 
of opposed blocks having nut engaging cavities in the opposed surfaces 
thereof. Means are provided for moving each upper block toward each lower 
block to grip a nut between the opposed cavities. Upper and lower blades 
are guided for movement through slots in each block whereby the blades may 
protrude into the cavities in the blocks. Means are provided for lowering 
the upper blade which upon engagement with the nut held between the upper 
and lower blocks will push the lower block downwardly against a spring 
thereby allowing the lower blade to project upwardly into the cavity in 
the lower block thereby cutting the nut by means of the upper blade and 
the lower blade. The upper and lower blocks and the upper blade are 
movable through a distance such that only the shell of each nut will be 
cut without inflicting any damage to the kernels of the nut. 
The present invention provides a new and improved method for cracking nuts 
comprising the steps of supplying a nut to a space defined between two 
cavities in upper and lower opposed blocks, lowering the upper block to 
hold the nut between the opposed blocks, lowering an upper blade through a 
recess in the upper block into engagement with the nut along the center 
line of the cavity in the upper block thereby pushing the lower block 
downwardly by means of the force exerted thereon through the nut held 
between the upper and lower blocks whereby a fixed lower blade will 
protrude through a recess formed along the center line of the cavity of 
the lower block, cutting the nut with the upper and lower blades at the 
same time until the blades are a specified distance apart and returning 
the upper and lower blocks and the upper blade to its original position to 
permit removal of the nut. 
The foregoing and other objects, features and advantages of the invention 
will be apparent from the following more particular description of a 
preferred embodiment of the invention as illustrated in the accompanying 
drawings.

DETAILED DESCRIPTION OF THE INVENTION 
The nut cracking machine as shown in FIG. 1 includes a hopper 1 adapted to 
hold a plurality of nuts 2. An endless slat conveyor 3 is guided for 
movement about a plurality of guide rollers 27 and a guide plate 26. The 
upwardly moving reach of the conveyor belt forms one wall of the hopper 1. 
The slat conveyor 3 is comprised of a plurality of slats connected 
transversely between two endless chains 6 with each slat having a 
plurality of cylindrical openings 4 extending therethrough in a row 
transverse to the direction of movement of the conveyor. Thus, as the 
conveyor 3 moves upwardly in the direction of the arrow A as shown in FIG. 
1, a nut 2 will be located in each cylindrical opening 4 and supported 
therein by means of a plurality of elongated flat guide plates 5 
positioned beneath the conveyor from the hopper 1 to the nut cracking 
apparatus. The conveyor 3 is driven intermittently by suitable driving 
means (not shown). Should additional nuts be conveyed upwardly by the 
conveyor other than those located in the openings 4 a brush 7 is mounted 
for rotation in the direction of the arrow B opposite the guide plate 26 
for returning the excess nuts to the hopper 1. 
A plurality of nut cracking bodies comprised of upper and lower blocks, 
upper and lower blades and hydraulic actuating means are disposed in a row 
parallel to the slats 3. The number of nut cracking assemblies is equal to 
the number of openings 4 in the slats 3. 
As best seen in FIG. 3, the nuts 2 are carried along the upper surface of 
the guide plates 5 by means of the slats 3 until the nuts reach the lower 
blocks 13 of the nut cracking apparatus. Each lower block 13 is normally 
biased upwardly by means of a spring 19. The upper surface of each lower 
block 13 is provided with a cavity 11 in the upper surface thereof having 
a slot extending therethrough in the direction of movement of the 
conveyor. A lower blade 8 is secured in a fixed position to each apparatus 
and extends upwardly through each slot in each cavity 11. The lower block 
13 is normally biased upwardly to the position shown in FIG. 3 by the 
spring 19 and the upward movement thereof is limited by the engagement of 
the pin 31 in the slot 32 in the block 13. With the block in the position 
shown in FIG. 3 the lower blade 8 is recessed within the slot formed in 
the cavity 11. 
When a slat 3 is moved into position over the lower blocks 13 with the 
openings 4 in alignment with the cavities 11, a suitable detector such as 
a phototube, or a microswitch (not shown) initiates the operation of an 
oil pressure pump 12 which supplies oil under pressure to each cylinder 14 
to move the associated upper block and blade assembly downwardly as shown 
in FIG. 1. Each upper block and blade assembly is comprised of an upper 
block 10 having a cavity 15 in the lower recess thereof adapted to engage 
a nut 2. The upper block 10 is biased in the downward direction by a 
spring 18 relative to the piston member 14. The block 10 is mounted for 
limited movement relative to the piston 14 by means of a pin 41 and slot 
42 similar to the pin and slot arrangement for the lower block. A blade 9 
is secured to each piston 14 for movement therewith and is adapted to 
protrude downwardly through an elongated slot in each cavity 15. Normally, 
when the piston 14 is in the raised position as shown in FIG. 3, the block 
10 is biased downwardly by the spring 18 to the limit permitted by the pin 
and slot connection 41 and 42 so that the blade 9 will not be protruding 
into the cavity 15. 
As mentioned previously, when one of the slats 3 is in position so as to 
place a row of nuts 2 in the appropriate lower recesses 11 formed in the 
lower blocks 13, an oil pump switch is energized to initiate the operation 
of each cylinder to extend the piston 14 thereof downwardly as viewed in 
FIG. 3. The downward movement of each piston 14 will bring the upper block 
10 with the cavity 15 into engagement with a nut so that a nut will be 
held between each pair of upper and lower blocks. Further downward 
movement of the piston 14 will cause the lower block 13 to move downwardly 
against the force of the spring 19 due to the downward pressure exerted on 
the nut 2. The lower blade 8 will then penetrate upwardly through the slot 
in the cavity 11 so as to engage the nut 2. The pressing of the nut 2 by 
the upper blade 9 is continued so that the upper blade 9 and the fixed 
lower blade 8 penetrate into the shell of the nut by a distance equal to 
the thickness of the shell. Thus, the nut shell will be divided into two 
pieces without damaging the kernal of the nut. The cutting distance of the 
blades relative to the nut 2 corresponds to the distance between the 
nondetecting position X of the switch 17 corresponding to the tip end of 
the metal detection strip 16 provided on the side wall of the upper block 
10 at a point where the downward movement of the upper block 10 is stopped 
as shown in FIG. 4 and the detecting position Y of the switch 17 
corresponding to the tip end of the metal detection strip 16 provided on 
the side wall of the upper block corresponding to the dead point where the 
downward movement of the upper blade 9 is stopped as shown in FIG. 4. When 
the tip end of the metal detection strip 16 reaches the detecting position 
Y of the switch 17, the flow of oil in the cylinder 14 is reversed to 
raise the upper block 10 and the upper blade 9 to their original positions 
as shown in FIG. 3. When the blade 9 moves upwardly, the upper block 10 
initially moves downwardly under the force of the spring 18 to the limit 
determined by the pin and slot connection 41 and 42 and subsequently the 
blade 9 and block 10 will move upwardly together. Simultaneously, the 
lower block 13 is moved upwardly by the spring 19 so that the lower blade 
8 will be effectively retracted from the cavity 11. As soon as the upper 
block 10 and the lower block 13 of each apparatus return to their original 
positions, the slat conveyor 3 accommodating the cracked nuts is conveyed 
intermittently for a specific distance so that the kernel 20 and the 
divided shells 21 drop downwardly from the cylindrical openings in the 
slat 3 as shown in FIGS. 1 and 3. 
The upper block 10 and the upper blade 9 are shown in detail in FIG. 5 and 
the details of the lower block 13 and the lower blade 8 are shown in FIG. 
6. The base portion 22 of the fixed blade 8 is provided with tapered sides 
as shown in FIG. 6 to facilitate the downward removal of any finely 
divided pieces of shell. Both the upper blade 9 and the lower blade 8 have 
a V-shaped notch 24 in the upper edge thereof defined by the angle .alpha. 
as shown in FIG. 7. The angle .alpha. should be chosen from the range 
between 120.degree. and 160.degree. in order to assure the proper cracking 
of the shell into two pieces. As shown in FIG. 8 the cutting edge of the 
blade is beveled on opposite sides of the blade with the beveled surfaces 
being separated by an angle .beta. which is approximately 80.degree.. When 
the angle .beta. is less than 80.degree. the blade is easily broken by 
repeated cracking of nuts and the cutting edge of the blade enters into 
the shell without separating the shell into two pieces. This frequently 
leads to damage of the kernel. Furthermore, if the angle .beta. is greater 
than 80.degree. the shell is not properly divided into two pieces. If a 
pressure higher than that required is applied in order to crack the shell, 
the entire shell tends to be crushed and scattered and the kernel damaged. 
Accordingly, it is necessary to maintain the angle .beta. at approximately 
80.degree.. As best seen in FIG. 8, the upper edge 25 of the blade 24 
should be cut to define a flat portion having a width W which will prevent 
abrasion of the edge. If the width W of the flat part is less than 0.5 mm 
the upper edge 25 is easily worn away. If the width W is longer than 0.5 
mm, the cracking requires a much higher pressure which is apt to shatter 
the shell with the possibility of damage to the kernel. Accordingly, the 
upper edge 25 of the blade 24 is cut flat and is provided with a width of 
approximately 0.5 mm. 
When the nuts such as walnuts or macadamia nuts are cracked by the process 
according to the present invention the shells can easily be divided into 
two pieces automatically and continuously without crushing and scattering 
the shell. Furthermore, the shells and kernel can be taken out without 
damage and the kernels can be easily separated from the shells. In the 
case of nuts having an even surface such as macadamia nuts, the shells can 
be divided equally in halves because the upper blades and the lower blades 
are disposed opposite each other in the same planes which in turn is 
coincident with the center of the nut. 
While the invention has been particularly shown and described with 
reference to a preferred embodiment thereof, it will be understood by 
those in the art that various changes in form and details may be made 
therein without departing from the spirit and scope of the invention.