Apparatus for granulating material

An auger feed granulator having a cutting chamber, the cutting chamber having a rotating knife assembly which traces a cutting circle which intersects the envelope defined by the auger. The rotating knife assembly engages and removes material carried into the cutting chamber by the auger. The knife assembly axis is offset from the auger axis. Stationary knives are provided adjacent the rotating knife assembly, as well as a removable screen having a selected mesh size which coacts with the rotating knives to determine the granule size of the material which exits from the machine. The screen is mounted on one side of the granulator and preferably has a radius of curvature the same as the radius of the circle traced by the rotating knife assembly. Lastly, the granulator is mounted on a base provided with a jack screw for tilting the granulator to any desired position without changing the relationship of the working parts of the granulator to each other.

This invention is directed to auger feed granulators, and more particularly 
to auger feed granulators useful in granulating hot plastic material just 
after release from a mold or die. 
Conventional auger feed granulators generally comprise a hopper containing 
an auger which is used to move material directly from a mold or die to the 
granulator. The granulator is provided with a cutting chamber into which 
either the auger or the shaft on which it is mounted projects to insure 
the feed of plastic or other material into the cutting chamber. 
The rotatable knife assembly is conventionally positioned below the auger, 
and a plurality of stationary knives are embedded in the cutting chamber 
housing adjacent the rotatable knife assembly. The stationary knives coact 
with the rotating knives and cut or break up material fed to the cutting 
chamber by the auger. 
In the prior art granulators, the rotating knives were generally positioned 
well below the auger. Plastic material reached the rotating knives only if 
the material fell from the auger by dint of its own weight. 
In addition to the foregoing, the stationary knives mounted on each side of 
the rotating knife assembly, were generally horizontally aligned and 
tended to retain plastic material above the rotatable knife assembly. The 
result was noisy granulator operation and a lower material output than 
would normally be expected. 
Although plastic has been used in the above description as the material for 
which the granulator is used, it is to be understood that the granulator 
can be used with any material subject to granulation, such as leather, 
wood, and nonplastic material. 
In the prior art granulators, the auger position has generally been 
vertically above the rotatable knife assembly. This has occasioned the use 
of a shallow curvature screen positioned vertically below the rotating 
knives. 
The conventional auger fed granulators described above have proven to be 
inadequate in many respects. First, when an auger fed granulator is used 
to feed hot material from the mold or die to the granulator, it has been 
found that the material, which generally comprises sprues and runners from 
a multiple cavity die, wraps about the shaft of the auger. Due to the fact 
that the material is hot, it can readily assume this bent position, wind 
about the shaft, and in essence remain bound to the shaft by its shape 
after the material has been advanced into the cutting chamber. 
In conventional granulators, the material does not readily release from the 
shaft. It will often continue to build up on the shaft until the machine 
jams. When this occurs, it becomes necessary to enter the machine to 
remove the build up. Removal techniques generally comprise the use of a 
hack saw or other manually operated cutting means, or the use of fire to 
burn the material off. Needless to say, the down time occasioned by this 
mass build up is undesirable and expensive. 
The use of a vertical cutting chamber with horizontal stationary knives has 
another undesirable feature. The action of the rotating knife assembly 
does little if anything to move the material fed into the granulator to 
the stationary knives. The material all too often remains trapped above 
the rotating knife assembly. This material is churned by the rotating 
knives, resulting in a rather high noise volume. The output of the unit is 
low and the existance of large amounts of material in the upper portion of 
the cutting chamber may contribute to the inability of the auger to strip 
itself of material wrapped about its shaft. 
Lastly, the use of a vertical unit tends to result in rather inefficient 
granulating action between the rotating knife assembly and the screen. 
Because granulators must be built quite low to the ground, very little 
room exists underneath the granulator for the installation of a screen. As 
a result, the radius of curvature of conventional screens has been 
significantly larger than the radius traced by the knife assembly in the 
granulator. Since granulator action depends to a great measure on the 
cutting or crushing action of the rotating knife assembly as it presses 
and crushes material against the screen, it is apparent that a screen 
having a larger radius of curvature than the cutting path of the knives 
premits knife action to be efficient only where the knife assembly is 
closest to the screen. 
A correlative problem is the removal of the material through the screen and 
into a system for returning the granulated material to the hopper of the 
molding dye for reuse. Relatively small space exists under the granulator 
for the installation of a return duct or transition piece. The granulated 
material must be moved at right angles to the direction in which it is 
released from the granulator. Build up of material may frequently occur in 
the duct due to the inability of the small duct size to handle the 
granulated material which exits through the screen. 
The use of a screen located directly under the granulator as described 
above also makes it rather difficult to install and remove the screen. In 
addition, the location of this screen directly below the granulator makes 
it extremely difficult to gain entry to the innards of the granulator for 
cleaning and servicing. 
In accordance with the present invention, an auger fed granulator is 
disclosed in which the auger shaft continues through the cutting chamber. 
The lower portion of the cutting chamber contains a rotating knife 
assembly which is offset to one side of the auger axis. In additon, the 
cutting path traced by the rotating knife assembly intersects the envelope 
defined by the auger. 
It has been found that offsetting the rotating knife assembly and having 
its cutting path intersect the auger envelope effectively prevents any 
material build up from occurring on the shaft of the auger. Hot material 
fed directly from a conventional mold or die frequently wraps about the 
shaft of the auger. It has been found that the rotating knives, when 
positioned to intersect the auger envelope, will contact the material 
contained on the shaft before any significant amount of build up has 
occurred. It is believed that the rotating knives grip the material on the 
auger shaft and pull it down into the cutting chamber where it is 
subsequently cut or broken up. 
In a preferred form of the invention, the auger shaft is placed in the 
upper portion of the cutting chamber and the rotating knife assembly is 
placed in the lower portion of the cutting chamber. The lower portion is 
offset from the upper portion to create a "dog leg" lower portion. At 
least one stationary knife is mounted in this lower "dog leg" portion 
which comprises a downwardly sloping wall. Material removed from the auger 
shaft falls onto the downwardly sloping wall and is moved by gravity, or 
funneled, to the stationary knife which is mounted in the sloping wall. 
The rotation of the rotating knife assembly tends to further force the 
material against the stationary knife, thereby obviating the rather large 
amount of free floating material encountered with the horizontally 
positioned knives of the prior art. 
In addition to the foregoing, it has been found that the screen through 
which the granular material is pushed by the rotating knife assembly may 
be mounted to one side of the unit. In doing so, the radius of curvature 
of the screen may be made substantially equal to the radius of the cutting 
path traced by the rotating knife assembly. Sizing or crushing action then 
occurs in a sizing or crushing region which comprises substantially the 
entire length of the screen. As a result, the output of the unit is 
materially increased. In addition to the foregoing, the side mounting of 
the screen permits easy installation and removal as well as easy access to 
the interior for cleaning and storage, a feature not found in the prior 
art vertical units. 
In accordance with still another aspect of the present invention, the 
granulator is mounted on a base plate which is in turn mounted on a dolly. 
The base plate is pivotable with respect to the dolly to permit the hopper 
to be lowered or raised in accordance with the height of the mold or die 
under which the auger is to be placed. Prior art units have generally 
lacked this feature or provided a pivotable hopper assembly which would 
result in a change of the angle of the auger with respect to the rotating 
knife assembly. By pivoting the base plate to which the granulator is 
mounted, the relationship of the auger to the other operating parts of the 
granulator remains unchanged.

Referring now to FIG. 1, the numeral 10 denotes an auger mounted in a 
trough 12 and having a hopper 14 for receiving material released from a 
molding press or die. 
The auger feeds the material directly to the granulator denoted generally 
by the numeral 16. Preferably, the auger flights are spaced from each 
other sufficiently to prevent substantial compacting of the plastic or 
other material as it is fed to the granulator. 
The hopper is adapted to receive the unused or waste plastic from the 
press. The plastic is generally in the form of interconnected sprue and 
runner assemblies. The size of these assemblies will vary according to the 
particular molds. These can be large and may frequently tend to wrap about 
the shaft 18 of the auger as they are fed to the granulator 16. 
As shown most clearly in FIG. 3, breaker bars 20 are positioned along the 
trough 12 in order to keep the material fed to the hopper, which is 
generally still quite hot, from adhering to the side walls of the trough. 
Rotation of the auger generally feeds the material into the bottom of the 
trough adjacent the breaker bars. The rotational force imparted to the 
material moves it against the breaker bars which serve to prebreak the 
material, thus serving to prevent the material from adhering to the walls 
of the trough or jamming the apparatus. 
As can be seen most clearly in FIG. 2, the auger 10 ends adjacent the 
cutting chamber 22 in the granulator. Auger shaft 18 continues through end 
wall 24, and terminates in drive means 26. Material fed to the cutting 
chamber by the auger is moved into the cutting chamber along the shaft 18 
by the pushing action of the preceding auger flight. 
The cutting chamber is best seen in FIG. 3. Two different sized auger are 
shown. For commercial units, the smaller auger may generally be six inches 
in diameter and the larger auger eight inches in diameter, of course, only 
one auger is present at any one time. Two are shown to illustrate the 
universal nature of the invention and its ability to adapt to different 
sized augers without destroying its function. Breaker 20' is used for the 
narrower trough 12' employed with the six inch whereas breaker 20 is 
employed with the larger trough 12 employed with the 8 inch auger. 
As shown in FIG. 3, the cutting chamber 22 is comprised of an upper portion 
28 and a lower portion 30. The lower portion 30 is defined by the angled 
side walls 32, 34. 
The upper housing 28 contains the shaft 18 of the auger whereas the lower 
housing 30 contains a rotatable knife assembly generally denoted by the 
numeral 36. 
The rotatable knife assembly comprises a shaft 38 to which a rotatable 
block 40 is fixed for rotation. Three arms 42 are depicted, each arm 
carrying a knife blade 44 at the edge thereof. The knives are angled with 
respect to the horizontal as shown in the drawing for purposes to be 
described below. 
The cutting circle traced by the rotating knife assembly intersects the 
envelope of the auger 10. For an eight inch auger, the envelope diameter 
will be 8 inches. The envelope will be six inches for a six inch auger. In 
the preferred embodiment auger 10 does not project into the cutting 
chamber. However, shaft 18 runs through the cutting chamber and will 
support or carry forward a substantial amount of the material fed into the 
cutting chamber by the rotating auger. 
It has been found that designing the rotatable knife assembly so that its 
cutting path intersects the auger envelope tends to insure that the knife 
will engage and pull off material wrapped about the shaft 18 which would 
not have released by itself. Buildup on the shaft does not occur, and 
granulator jamming is prevented. Thus, granulator down time is avoided 
along with consequent down time of the molds and dies which feed the 
granulator. 
Housing side wall 32 slopes downwardly and to the side of the shaft 18. 
Positioned along the side wall 32 is a first stationary knife bar 46. The 
position of the knife bar 46 in the cutting chamber is adjustable via a 
conventional nut and bolt assembly generally denoted by the numeral 48. It 
has been found that the clearance between knives 44 on the rotatable 
assembly and knife bar 46 should preferably be about 0.005 inch to provide 
for initial crushing of the plastic material. However, spacings greater or 
smaller than 0.005 inch can be used if desired. Plastic or other material 
is moved between the stationary and rotating knives and is broken up into 
smaller fragments. For best results, an additonal bar knife 46 may be 
positioned directly opposite the first bar knife defining a region between 
them in which additional cutting, sizing or crushing action can take place 
as will be described more fully below. 
A cutting region 50 is provided which is defined by side wall 32, rotating 
knife assembly 36, and the bar knife 46. The cutting region decreases in 
size towards the bar knife 46. Material removed from the shaft 18 tends to 
accumulate in cutting region 50 and is moved by gravity and by the 
rotating action of knives 44 down towards the stationary bar knife 46. All 
material contained in the region 50 tends to be quickly and efficiently 
moved past the stationary knife 46. Through-put of the granulator is 
increased over prior art designs in which the stationary knives were 
placed horizontally and directly beneath the auger feed. In the prior art 
designs, material tended to remain above the rotating knife assembly, and 
only the rotating action of the knives could effect movement of the 
material to the stationary blades. Aside from inefficiency, the prior art 
units were also quite noisy, whereas the granulator of the present 
invention is not. 
Positioned to one side and comprising the bottom portion of the lower 
housing is a screen denoted by the numeral 52. The screen is generally 
made of metal having holes 54 punched or drilled therein, the holes being 
determined by the size of the granulated material one wishes to remove 
from the granulator. 
The radius of curvature of the screen used in the present invention is 
substantially the same as the radius of the cutting path of the rotating 
knife assembly 36. The lower part of the housing which surrounds the 
screen comprises a boxed-like shaped projection 60; the upper end is 
removably attached by any suitable means such as the bolt and nut 
connection 63, preferably on each side of the housing. The box-like shaped 
projection is pivoted to the lower housing 62 and can be dropped down to 
the lower dotted line position shown in FIG. 3. With the box-like 
projection in this position, the screen can be easily and simply removed, 
thereby allowing access to the entire interior of the granulator. To 
further aid access to the interior, the top 64 may be made removable by 
simply removing the plates 66 and 68, which are mounted to the granulator 
housing by conventional fastening means 69. 
Sizing or crushing action occurs between the rotating knives 44 and the 
screen. As can be readily appreciated, the screen 52 comprises an arc 
length of approximately 180.degree. and has a radius of curvature 
substantially the same as the cutting circle traced by the rotating knives 
44. Sizing or crushing action between the knives 44 and screen 52 takes 
place over the entire arc length, or circumference, of the screen. In 
contrast, the prior art granulators tended to use screens having a shallow 
curvature. As a result, sizing or crushing action was restricted to the 
region in which the knives were in close proximity to the screen. Sizing 
or crushing action provided by screen 52 occurs over a much longer 
surface, obtained by using a screen having a radius of curvature equal to 
the cutting path radius of the knives 44. 
Two stationary knives or cutting bars 46 have been shown. More or less can 
be used as desired. In addition, three rotating knives 44 have been shown. 
Again, more or less can be used as desired. 
Referring now to FIG. 4, a conventional drive for the rotating knife 
assembly and the auger is shown. The auger drive is generally denoted by 
the numeral 70 and consists of a gear 72 to which a chain 74 is mounted. 
The chain drives a second gear 76 which in turn drives shaft 18 of the 
auger assembly. 
The rotating knife assembly is driven by a conventional motor denoted by 
the numeral 78. 
The drives described above are conventional and further description is 
deemed unwarranted. 
Referring again to FIGS. 1 and 2, the granulator is seen mounted on a dolly 
80 which comprises a mobile base 82. A base plate 84 is pivoted at 86 to 
the mobile base. A jack screw comprising bushing 90 is pivotally mounted 
in the bushing 88 which in turn accepts screw 92 therein. The collar 94 is 
pivotably mounted to arm 96 which is integral with the mobile base. 
Rotation of the screw 92 will move the base plate up and down as shown in 
the drawing in order to reorient the entire granulator with respect to 
horizontal. This movement is desirable in order to lower the auger and 
hopper as shown in FIG. 1 in dotted lines to permit positioning of the 
assembly under "low to the ground" presses. 
Referring now to FIG. 5, the box-like shaped projection or cover 60 is 
shown at one side of the auger fed granulator. A return duct or transition 
piece 98 is shown which receives material exiting through the screen 52. 
The material is moved by a conventional fan assembly 110 through duct 100 
and into duct 102 for return to feed hopper 106. The feed hopper 106 feeds 
the material directly into preheat chamber 108 for the mold. In this 
manner, granulated material which would otherwise be wasted is returned to 
the molding process. 
Many modifications may be made in and to the above-described embodiments by 
those of ordinary skill in the art to which this invention pertains. It is 
intended to cover all such modifications which fall within the spirit and 
scope of the invention as defined in the claims appended hereto.