CA1064759A - Apparatus for preparing animal food pellets - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Apparatus for preparing animal food pellets wherein cooked mash under atmospheric pressure is forced through a die wherein the mash has been cooked under superatmospheric pressure. More specifically, the apparatus provides means defining a continuous flow path for mash including conditioning means in said path for cooling 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 is the range of about 1 psi to about 25 psi. The unique pressure cooking of the mash eliminates the operator guesswork of prior art conditioning steps and results in a mash which is dearated and considerably more plastic.

Description

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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 . ~ ~, .

~ 647sg 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 1~47~9 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 jl/ ~ -3-~ ,:

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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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jl/ -3a-' ~647~9 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 . .

_ ~ _ ~ 64~59 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 -~ OÇi4759 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 ~ 1~64759 ~ .
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%.
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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 ' ' ' , ' .

1(~6~75'9 ~ 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.

dg/~' -8-- ~6~7591 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 _ 9 _ - ~G4759 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.
, - 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 36~75~ `
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 i ~~ ~ 36~ and.a uni~orm diameter portion 41 within the cylindrical - 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 ;

, ~ L06~59 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.

1~647~j9 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 ~ 647059 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 .

1~6~7~9 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'.
' 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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Claims (4)

The embodiments of the invention in which an exclusive privilege is claimed are

1. 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 character-ized 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.

2. The apparatus of claim 1 in which said con-ditioner means includes a generally S shaped conditioner unit having generally parallel top, middle and bottom legs, said top leg constituting a feeder casing and having a mash inlet opening adjacent one end and a rotary eseal at the other end, said other end of said top leg being connected to one end of said middle leg, feed screw means in said feed casing for advancing mash from said inlet opening against said rotary seal, the other end of said middle leg being connected to one end of said bottom leg, advancing means for mash in said middle leg, a second rotary seal positioned at the other end of said bottom leg, discharge screw means in said bottom leg for advancing mash against said second rotary seal, means for introducing steam into said middle leg and means for venting air from said conditioner unit at a point inter-mediate said rotary seal, means for turning said feed screw and said discharge screw and means for operating said rotary seals independent of each other and independent of the means for turning said screws.

3. The apparatus of claim 2 in which said means for turning said screws are located at one end of said apparatus and said means for operating said rotary seals are at the other end of said apparatus.

4. In a method of preparing animal food pellets wherein cooked mash under atmospheric pressure is forced through a die, the steps of cooking 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 thereafter 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).