Note: Descriptions are shown in the official language in which they were submitted.
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IL064759
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BACKGROUND AND SIJ1~1ARY OF INVENTION:
This invention relates to an apparatus for and a
method of preparing animal feed pellets and, more particularly,one employing unique pressure cooking for the mash which becomes
the animal food pellets.
For many years, various cereal grains, plant and animal
proteins, roughage products, liquids, and other miscellaneous
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ingredients have been mixed together to form a mash which was
relatively aerated. The mash normally has been fed from a bin
holding the bulk mash through a variable screw feeder to an
atmospheric conditioner or cooker. Because of the different
ingredients and the amounts ther~of in various formulas
of animal food, different rates of mash introduction and different
amounts of moisture addition were required. Further, when the
pelleting mash was conditioned with steam under atmospheric
pressure, the different formulations required different temp-
10 eratures for proper pelleting. This resulted in temperatures ofthe mash exiting from the conditioner varying from room temp-
erature to 212 )the maximum attainable) and an added moisture
varlation of from 0 to 10% (or a total moisture in the mash from
7% to 22%). Therefore, conditioning of the mash for pelleting has
been an art as contrasted to a science -- and one which has been
difficult to master because of the varied demands of temperature
and moisture required by each of the formula combinations of
ingredients.
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According to the prior art, after the mash had been
20conditioned, i.e., cooked and/or moisturized at atmospheric
pressure, it was introduced into a pellet mill. Pellet mills
normally have employed a rotating annular die into which the mash
is introduced axially and forced under the action of stationary,
idler rollers through a plurality of die orifices. Thus, the
mash, under atmospheric~pressure, was subjected essentially
to a tangential force relative to the movement of the annular
die. The conditioned mash traveled at different velocities
causing the high velocity, coarse particle mash to be at the
lagging side of the die orifice and the slow moving, fine particle
30mash at the leading side. The high velocity of the mash at the
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lagging side resulted in poor partlcle adherence, evidenced
by fractures in the issuing square or round rods -- the die
out-put being transversely severed to form round pellets or
cubes.
According to the invention, the conditioned or cooking
of ~he mash is achieved at a controlled steam pressure above
atmospheric which results in a number of advantages. Not
only does it eliminate the guesswork heretofore characteristic
oE the conditioning step but it results in a mash which is
deaerated and considerably more plastic, making it possible
for the roll and die of the pellet mill to achieve a better
"bite", thereby changing the through-put of the ingredients
through the die orlfices. This results in achieving a
substantially uniform consistency across any transverse
plane and substantially eliminates the heretofore disadvantageous
fractures along the lagging side of the pellet rods.
In one particular aspect the present invention provides in
apparatus for continuously preparing animal food pellets, means
defining a continuous flow path for mash including conditioning
means in said path for cooking said mash under super-atmospheric
pressure, means next in said path for tangentially forcing said
mash through orifices of a rotating die to form deaerated rods
of substantially uniform consistency across successive transverse
planes and characterized by the substantial absence of fracture
on the lagging side of the ribbon and means next in said path
for transversely severing the ribbons to form pellets, said
conditioner means being constructed and arranged to confine the
mash in a steam atmosphere in the range of about 1 psi to about
25 psi.
In another particular aspect the present invention provides
in a method of preparing animal food pellets wherein cooked
mash under atmospheric pressure is forced through a die, the
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steps of coo~ing said mash under super-atmospheric pressure,
reducing the pressure on said mash to atmospheric, radially
forcing said mash through orifices of a rotating die to form
deaerated rods of substantially uniform consistency across
successive transverse planes and characterized by the substantial
absence of fractures on the lagging side of the rod and there-
after transversely severing the rods to form pellets, said
cooking step being performed by confining the mash in a steam
atmosphere in the range of about 1 psi (gauge) to about 14 psi
(gauge).
- Other advantages and objects of the invention may be
seen in the details of the ensuing specification.
DETAILED_DESCRIPTION:
The invention is described in conjunction with the
accompanying drawing, in which --
- Fig. l is an elevational view, partially in section and
partially schematic showing apparatus employed in the practice
of the invention;
Fig. 2 is an enlarged fragmentary perspective view of
the interior of the pellet mill annu]ar ring seen in the lower
left hand portion of Fig. l;
Fig. 3 is a side elevational view of a 11/64" diameter
pellet or rod portion produced according to the prior art
procedures;
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FIG. 4 is a view similar to FIGS. 3 but showing a 11/64''
pellet rod produced according to ~he teachings of this invention;
FIG. 5 is an elevational view on enlarged scale of
the conditioner portion of FIG. l;
t FIGS. 6, 7 and 8 are views taken along the lines
6-6, 7-7 and 8-8 respectively of FIG. 5; and
FIG. 9 is a sectional view of the conditioner of FIG. 5.
' In the illustration given, and with reference to
FIG. 1, mash (so indicated), is fed through a hopper or bin B
10 into a conditioner unit 10, more particularly the variable speed
feeder port-ion 11 ~hereof. The mash is adva,nced to the right
(in the illustration given) in a plug-type flow developed by a
pressure seal member 12. The seal,member 12 may advantageously
be of the positionable cone variety as described in detail
in Patent 3,246,594. By the variable screw feeder 11 pushing
, the mash against the pressure seal 1~, a solid plug of mash i's
, developed in the seal area 13. The conical element of the seal
12 rotates and is equipped with stud-like projections or
breaker bars which granulate the plug of mash into,small
20 particles 90 that each parti'cle can be wetted.
Thereafter, the mash particles enter the con-
ditioner pressure chamber 14 wherein the mash particles are
subiected to a super atmospheric'pressure schematically re-
presented by the introduction of steam. During this phase
of the conditioning, the super atmospheric pressure is main-
tained through the provision of a second seal 15, this being
at'the end of another variable screw feeder 16. Between the
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seals 12 and 15, the mash is advanced and tumbled by
' means of a paddle mixer conveyor 17 and the var~able screw
feeder 16. Controlled escape of air is achieved at 14a which
results in the mash being substantially deaerated. An adjustable
valve (see FIG. 9) or similar regulatable device communicates
with the atmosphere so that the air driven out-of the mash
particles by the steam has a place to escape. The'mash there-
fore is cooked through and deaerated prior to-pelletizing.
After the ,conditioned mash proceeds beyond the
; 10 second sealed area 18 (developed by the conical element of the
seal 15), it is particula~ed again by breaker bars provided
on ~he rotating conical element of the seal 15 and flows down
-a chute or spout 19 to a paddle feeder chamber 20. In the
chamber 20 the paddle feeder 20a advances the mash particles
generally axially into the pellet mill generally designated 21.
The chute 19 and chamber 20 are at atmospheric pressure as
represented by the arrow l~a -- any steam pressure being ,
reduced b~ ieakage between the conf:ronting flanges of the chute
19 and the feeder chamber 20. '
~Q ' As can be appreciated from a comparison of the lower
left hand portion of FIG.'l, and a further consideration of
FIG. 2, the active elements'of'the peIlet mill include a
rotatable mounted annular die 22 which is equipped with a
plurality of orifices or passages 23. Internally of the
rotatable die 22 a plurality of idler rolls 24 are provided
which are'turned by virtue of frictional engagement with the
interior of the annular die 22 and serve to force the mash
through the orifices 23,
.
' Power for rotating the die 22 is transmitted by
30means of a gear 25 from a motor (not shown) whereas power for -
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turning the paddle feeder is provided by a motor 26 through a
belt drive 27. This portion of the apparatus, i.e., the paddle
feeder and pellet mill is commercially available from a number
of different sources such as Sprout-Waldron ~ Company, In~,
of Muncy, Pennsylvania; Gali~ornia Pellet Mills Company of
San Francisco, California; and Landers Machine Company of
Fort Worth, Texas. Such mllls provide about twice the output
of a similarly powered extruder, i.e., 7-8 tons versus 3-4 tons
at 100 hp.
The rods or ribbon-like streams issuing ~rom the
orifices 23 are transversley severed by knives or like shear-
ing elements (not shown) into pellets of discrete length. An
embodiment of a pellet made according to the instant invention
is illustrate-d in FIG. ~ which is seen to be well knit or
integrated as exemplified by the absence of fractures or
cracks such as is found at 28 in the prior art pellet shown
in FIG. 3.
T E PRIOR ART
As mentioned previously, mash of a particular formu-
lation was fed into an atmospheric conditioner chamber by a
; 20 ~ariable screw feeder such as that designated by the numerai 11
in FIG. 1. The screw feeder was designed to feed the desired
; amount of mash to the atmospheric conditioner at a variable rate
because each formula usually required a different rate of mash
advance. The conditioner was made up as a mixer having a constant
speed. The conditioner served as a condenser in which
the cold mash caused the steam to condense whereby the
temperature and moisture content of the mash was ralsed. Normally
steam was fed into the container through a series of
steam jets. Since the conditioner was open and not sealed,
30 the conditioning was done at atmospheric pressure so 212 was
the top temperature that could be reached. The moisture addition
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depended upon the temperature of the mash entering the
conditioner chamber and the exiting temperature of the mash
required for the pelleting. According to the prior art, each
formula required a different temperature of the mash from the
conditioner, such mash temperatures varying from room to 212F.
with an added moisture variation of from 0% to 1OO/J or a total
moisture in the mash of from 7% to 22%.
.
As indicated previously with respect to the pellet
- mill 21, the rolls 24 were turned by the friction of the . 10 annular die 22. Due to the rolls 24 being tight enough against
the interior cylindrical wall of the annular die 22 to cause
the roll 24 to turn, a biting effect was created which pushed
the conditioned mash through the orifices 23. The action of
the rolls 24 against the annular die 22 resulted both passing
. the mash through the orifices 23 to produce the pellet
ribbons and simultaneously, a reciprocating action, i.e., in and
; out of.the orifices 23 to cause an attrition-of the mash
particles. Normally, the die 22 was rotated but the different
designs required different speeds with the result that different
20 resistances were encountered in the various dies. This was
further complicated by the different shapes and sizes of
finished pelle~s to that of the normal range of speeds ranged
from 100 to 400 rpm -- further requiring an artistic handling of
what should have been a scientifically controllable process.
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. Further, different components of the conditioned
mash traveled at.different velocities because of the
interaction of the rolls 24 and the interior cylindrical wall
of the annular die 22. For example, the high velocity,
coarse particle mash appeared at the lagging or rear
30 side of the orifices 23 (as each passed a given point) because
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~ of the rotation of the die 22. On the other hand, the slow
moving, fine particle mash appeared at the leading or front side
of each orifice. The high velocity mash component produced less
adherent particles, resulting in fractures 28 which caused
pellets generated therefrom to fall apart and become fines.
Also, coarse particles as at 29 were much more prevalent.
THE INVENTION
According to the inventive procedure, the mash is
conditioned in a superatmospheric chamber defined at the ends
thereof by the seals 12 and 15. These conical seals serve to
arrest the flow of mash so as to develop a plug of discrete
length (in the direction of mash flow) and which is abraded by
suitable projections on the rotating conical seal members 12
and 15.
The conditioning is advantageously achieved by steam
under pressure of from about 1 psi to about 25 psi. By pressure
cooking the mash, the mash particles are cooked substantially
throughout (and deaerated) and this can be achieved in a period
of as little as about 10 second -- particle residence time in
the conditioner between the seals 12 and 15. As the pressure
cooked conditioned mass issues from the seal 15 in~o the atmos-
pheric pressure chute 19, the mash has been deaerated, and is
soft, sticky, hot and wet. As it enters into the roll and die
area of the pellet mill 21, a better "bite" of the mash is
achieved and the tangential forces are more effectlve in forcing
the mash through the orifices 23, particularly as a homogeneous
unit (or material having a substantially uniform consistency
across each successive transverse section). This applies to a
wide range of pellet sizes. Normally the pellets which result
from a square cross section orifice are designated cakes and
are popularly of the order of 3/4" to 1-1/4" on a side. Similar
diameter dimensions are achievable using circular cross section
orifices.
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Further, I have found that the inventive conditioning
of the pellets results in the pellets being less fragile --
even without the use of binding agents. This is advantageous
in reducing the cost of the animal feed pellets and permits
the use of the money heretofore spent on binders and the like for
more nutritional ingredients. In addition, more efficent use
is made of the power needed to advance the mash through the
conditioner -- pellet mill combination. It will be appreciated
that the power for rotating the annular die 22 is a quite
10 expensive form of power, i.e., electricity, as eontrasted to
the relatively cheaper power provided in the form of
- steam to the conditioner. Thus, it is additionally
advantageous to utilize the pressure cooking principle
in that not only is a superior product achieved, but at
less power cost.
Although the mechanism by which the invention
operates is imperfectly understood, it is believed that there
is a significant difference in the "bite" area between the rolls
24 and the interior cylindrical surface of the die 22. With the
20 atmospheric-conditioned mash, the individual particles were
cooked primarily on the outer surface causing the interior
of the surface to remàin hard and also retain entrapped air.
This type of particle could not be trapped easily between the
roll and die, causing the mash to be forced in and out of the
die orifices resulting in an abrading action of the ingredients,
requiring extra-power. The mash co~ld travel this in-and-out
path a number of times until trapped and thereby able to
overcome the resistance created by the length of the orifice.
Because of the different resistances in different sections of
30 the walls of the orifices 23, the mash traveled at different
velocities and thereby created diffeFent degrees of compaction
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and adherence along the length and at di:Eferent side segments
of the pellet ribbon rod. This resulted in non-uniform quality
and a tendency to fracture and generate fines.
On the other hand, with the cooking or conditioning
at super atmospheric pressure, binders heretofore deemed necessary
can be eliminated and replaced by such important and advantageous
ingredients such as fat, ureà and other important nutritional
agents. Further, because of the more plastic nature of the
deaerated mash resulting from pressure cooking, these
lOadvantageous ingredients are able to penetrate beyond the
surface of the mash particles, taking the place of the released
air.
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- Further, when the cooking was performed at atmospheric
pressure according to the prior art, operators of pellet mills
were forced to cook different feed`formulas as di~ferent
temperatures and moisture. Each formula haa a prescribed amount
of moisture and heat added by steam which, if exceeded, would
cause plugging. If not enough steam were added, excessive
power was required in the pellet mill or the output rate reduced.
20According to the inventive procedure, lt is possible to
pellet each formula at the same steam pressure resulting in
a mash of uniform consistency irrespective of formulation --
because o~ the combination of cooking throughout and
deaeration. This makes the operation much more readily amenable
to automation and reduced the need for special equipment and
knowhow.
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MECHANICAL DETAI~S
The conditioner unit 10 is seen in greater détail in
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FIGS. 5-9. As seen in FIGS. 5 and 9, the ~mit has generally
an S shape when viewed in front elevation. This S shaped
arrangement makes possible the positioning of the ~eeder
drives along one end as at 30, 31 and 32 (see the left hand
portion of FIG. 5) and the devices 33 and 34 for operating
the pressure seals 12 and 15, respectively, at the other
end (see the right hand side of FIG. 5~. The screw feeder
portion 11 (previously identified with respect to FIG. 1)
includes a tubular casing 35 which, at the drive end thereof,
10is equipped with a flanged opening 36 for com~.unication with
the bin B (compare FIGS. 1 and 5~. The casin~ 35 is trough-
shaped as at 37 (see FIG. 6~. Downstream of the opening
36, the casing 35 is cylindrical as at 38 (see FIG. 7).
The casing 35 houses a tapered feed screw 39 (see FIG. 9~.
In the ilIustration given the cylindrical porion 38 of the
casing 35 is a 10" nominal diameter~stainless steel pipe and
the screw 39 has a tapered portion as at 40 (under the opening
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- portion 38. Reference to FIG. 9 reveals that the screw 39
20terminates short of the conical seal 12 to provide a discrete
spacing 42. Thus, the seal 12 is operable independently
of the screw 39.
The conical seal l2 is advantageously constructed
of stainless steel and has disposed in a plurality of rows
around its conical surface a plurality of stud-like projections
or breaker bar elements 43. When the seal element 12 is
in the open position (shown in dashed line and designated by
the numeral 12'), it can be rotated by means of a hydraulic
motor 44 while being moved axially -- to the closed position
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sho~m in solid line -- by means of a hydraulic cylinder 45.
The combination of pressure on the seal element 12l and
rotation thereof, causes the elements 43 to abrade the mash
plug and ultimately permits the plug 12 to come into bearing
contact with the replaceable annular seat 46. The seat 46
is a stainless steel ring which is bolted to the chamber 14
by means of bolts 47 (see also FIG. 7).
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For the purpose of operating the seal 12, the casing
14 is equipped with a pedestal 48 (see FIG. ~) which supports
10 the hydraulic cylinder 45. The piston rod 49 of the cylinder
45 extends through a packing gland 50 supported about an opening
in the casing 14 and is pivotally connected as at 51 to the
hydraulic motor 44. The output shaft 52 of the hydraulic motor
44 is connected to a gear couplin~ 53 which in turn is connected
to the element 12. Omitted for th~ clearness of presentation
are the usual flexible hydraulic lines to the motor 44 and the
cylinder 45
~s pointed out previously, the provision of the seal
12 for the inlet 54 makes possible an isolation of the chamber
2014 from the upstream por~ion of the system -- thereby preventing
steam from bleading back to the feed casing 35 and even the bin B.
The presence of moisture can cause buildup of the mash on
the screw 39 and the interior walls of the casing 35 to
cause uneven feeding into the pressurized conditioner 14.
With the uneven feeding, there is a return to the tire
difficulties in handling a mash for pelletizing. With the
inventive arrangement, it is-possible to reproduce a desired
feed rate at a given feeder setting. The provision of the
seal 12 in the linlet 5~ also insures against the more vexing
30 possibility of a complete plugging of the feeder casing 35 --
with the attendant work of disassembly, clea~-out, etc.
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Through the inv~ntive arrangement wherein the
seal 12 is operable independently of the screw 39, it is
possible to shut down the equipment while retaining steam
pressure within the conditioner 14. Thus, the system depicted
lends itself to an advantageous automated pelleting operation.
, Further, without the independence of operation of the seal 12
and the screw 39, it would be necessary to rely upon an annular
- plug of mash to effect the seal rather than the advantageous
metal-to-metal contact (between the seal element 12 and the
10 seat 46) because the moment the screw 39 was stopped, the
seal 12 would also stop -- and thereby be unable to abrade the
annulus necessary to achieve the metal-to-metal seal.
The inventive arrangement includes a variable drive
on the seal 12 which-provides flexibility when varying production
- rates and varying material densities are encountered. It also
makes possible the application of pressure conditioning to
~¦ ` pellet mills where large numbers of startups and shutdowns
are required due to-the variety of iormulations processed. Still
further, it provides for narrow orifice openin~s, desirable to
20 minimize size of the product plug at the seal. This orifice
can be adjusted by varying the rotating speed of the seal plug
or element 12.
For a given feed rate and a given mash formulation,
there is no longer any need for artistry in production. Through
the provision of a position indicator 55 on the piston rod 49
(see the upper right hand portion of FIG. 9) and the provision
of a sGale 56 in combination therewith, the precise location
of the seal 12 relative to the seat 46 can be quickly ascertained.
Once the optimum setting of the seal is determined (in conj~mction
30 with a given rotational speed) a function of the hydraulic pressure
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to the motor 44, further runs can be quickly performed under
optimum conditions. ~ot only does the position indicator, i.e.,
the elements 55 and 56, show the location of the seal 12 at
all times (the seal being hidden within the chamber 14) but it
also informs the operator when a run has been completed as the
seal 12 moves to the closed position.
In the operation of the inventive apparatus,
mash which has bee~ compressed by virtue of passing
through the annular space between the seal 12 and the
10 seat 46 encounters steam pressure which is advantageously
introduced through a pipe 57 (see FIG. 5) communicating
with the interior of the-housing 58 constituting the middle
branch of the previously referred to S configuration. The
steam pressure within the chamber 14 causes air to be released
from the mash, the air advantageously exiting through the
vent 14a which is advantageously regulated by means of a
gate valve 59 (see the upper rlght hand portion of FIG.
S). The mash is tumbled and advanced within the housing
58 by means of a paddle mixer 17 and thereafter drops into
20 a discharge casing 59. Each of the casings 39 and 59 and
the housing 58 are equipped with suitable access openings as
at 60, 61 and 62, respectively (see FIG. 6).
Mash in the discharge casing 59 is advanced toward
the seal 18 by means of the discharge screw 63 (see FIG. 9).
The outlet seal 18 makes possible the maintenance of super-
atmospheric pressure within the conditioner chamber 14 and
thus makes possible a controlled, automated production of
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mash for pelleting. The seal 18 employs the same element for
operation thereof as does the seal 12. For e~ample, the
operating means 34 (see FIG. 5) also employs a hydraulic
cylinder as at 45'. As also seen in FIG. 9, the operating
means for the seal 18 includes a hydraulic motor ~4' which
rotates the conical element 18 when the same is moved under the
urging of the cylinder 45' from the 181 position to the closed
position -- when the same engages the ring seat ~6'.
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The discharge seal 18 is operable independently of the
lOdischarge screw ~3, much the same as the inlet seal 12 is
operable independently o~ the feeder screw 39. Thus, the
equipment can be shut down -- as far as through put of mash
is concerned while the seals continue to operate (and close).
This prevents the blowout of steam, important for operator
safety. This independence of oper~tion also provides a variable
orifice discharge which adapts the apparatus to variations in
- pressure and product flow rate, as might be occasioned by
chan~es in formulation, density, etc.
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