Multidie positive displacement metering apparatus and process

This apparatus provides positive displacement synchronized metering of pressurized food material to a plurality of dies using several positive displacement metering apparatus. The metering is provided by the energy of pressurized material itself, or, for more viscous material, it can be supplemented by a motor. Supplemental material can also be introduced along with the food material to modify the characteristics of the food material.

FIELD OF THE INVENTION 
The present invention relates to metering viscous food material to a 
plurality of extrusion dies. More specifically, this invention teaches the 
use of positive displacement metering to a plurality of extrusion dies. 
BACKGROUND OF THE INVENTION 
A number of food extrusion processes require an equal flow of material from 
a number of dies which are fed from the same die holder. If the flow of 
material is unequal then the resulting product streams are also 
non-uniform which is undesirable. This is particularly true if the food 
material is cut to a predetermined length with an estimated weight for 
packaging based upon the length, which is not unusual in extruded food 
packaging. 
A number of arrangements have been provided to attempt to provide equal 
amounts of food material from a number of dies with each die extruding the 
same quantity per unit time. Previous attempts have been directed to 
producing the same pressure on each die in an attempt to obtain the same 
quantity of extruded product per unit time. 
A example of the prior art, before an attempt was made to obtain equal 
pressure on each die, is shown in FIG. 1. Here extrusion apparatus 12 has 
a source of heated material introduced through pipe 32 into a manifold 26, 
which can be heated. Dies 18 are all connected to die holder 20, which has 
a conduit 21 opposite each die from die holder 20 into manifold 26. The 
result of this arrangement is shown in FIG. 1A with the resulting pressure 
in pounds per square inch (PSI) as a function of die location 13. FIG. 1A 
is also positioned opposite FIG. 1 such that the die locations of FIG. 1A 
all directly relate to the die 18 locations of FIG. 1. Since pipe 32 is 
centrally located the maximum pressure is also centrally located with a 
reduction in this pressure outwardly in both directions as shown in FIG. 
1A. 
An attempt to remedy this situation is shown in FIG. 2 where extrusion 
apparatus 14 has two pipes 34 feeding heated pressurized food material 
into manifold 28. Conduits 23 extend between manifold 28 to die holder 22 
opposite each die 18. The results of this arrangement is shown in FIG. 2A 
with the resulting pressure in pounds per square inch (PSI) plotted as a 
function of die location 15. FIG. 2A is also positioned opposite FIG. 2 
such that die 18 locations of FIG. 2A correspond to the die locations of 
FIG. 2. Since pipes 34 are spaced approximately one-third of the distance 
along manifold 28, two maximums essentially opposite pipes 34 occur, with 
a reduction in these pressures outwardly in both directions as shown in 
FIG. 2A. This is an improvement over the results of extrusion apparatus 12 
but the pressure of each die is still far from equal. 
An improved attempt to provide equal pressure on dies 18 is shown in FIG. 3 
with extrusion apparatus 16 again having only one pipe 36 feeding heated 
pressurized food material into manifold 30. Conduits 25 extend between 
manifold 30 to die holder 24 opposite each die 18. Here however each die 
18 has a valve 38 in connection 23 to die holder 24. Valves 38 permit 
adjusting the pressure on each die 18 independently. The results of this 
arrangement is shown in FIG. 3A with the resulting pressure in pounds per 
square inch (PSI) plotted as a function of die location 17. FIG. 3A is 
also positioned opposite FIG. 3 such that die 18 locations of FIG. 3A 
correspond to the die locations of FIG. 3. Here the resulting pressure is 
nearly equal at all dies because valves 38 have been adjusted to achieve 
this result. 
Even extrusion apparatus 16 does not produce the desired result of a 
uniform quantity of material extruded from each die 18 over any given time 
period. This results because the quantity being adjusted, namely pressure, 
is not the quantity which must be kept uniform, namely extruded material 
per unit time. Equal pressure on dies 18 will only produce equal flow if 
the material friction to and through each die remains identical, and if 
the material being extruded through each die has identical viscosities. 
Any difference in the temperature of a food material will result in a 
change in its viscosity, with lower temperatures resulting in greater 
viscosity. Dies 18 located at the ends of die holder 24 will receive 
material which has a longer flow path with a greater length of time to 
cool with a resulting greater viscosity, which will cause some of to 
adhere to the die intake reducing its size and increasing its friction. 
While a small differential is insignificant initially, the effects build 
up exponentially with time. Consequently, a small reduction in flow caused 
by lower temperature causing greater viscosity will result in the material 
being fed to that die flowing even slower, which increases the temperature 
differential even further. This builds up into a catastrophic failure 
quickly until the die is blocked completely. This is an inevitable result 
of any temperature differential in the material, and will always result in 
die blockage. Once even one die is blocked the die assembly must be 
disassembled and cleaned before it can be used further. These problems are 
multiplied when extruding multiple phases at one time, or when the 
material contains lumps of material of a size which can plug a die. 
Meisner, in U.S. Pat. Nos. 4,925,380 and 5,019,404 utilizes a scheme for 
manufacturing a multicolored aerated confection product utilizing 
multi-orifice extrusion system for extruding multiple strands of a 
confection material. These apparatus have the problems discussed above 
since no provision is made for metering equal amounts of material through 
individual dies. 
A number of apparatus utilize positive displacement metering of both 
plastic and food materials to extrusion apparatus obtain a uniform 
product. These include Fox, U.S. Pat. No. 4,336,213; Rahlfs, U.S. Pat. No. 
4,171,193; Fritsch, U.S. Pat. No. 3,649,147; R. Levison et al., U.S. Pat. 
No. 3,078,513; H. Corbett, U.S. Pat. No. 2,680,880; and Marin, U.S. Pat. 
No. 5,182,066 
All of these positive displacement metering apparatus drive only a single 
extrusion die. There is no teaching of using a number of synchronized 
positive metering apparatus to provide a plurality of uniform and equal 
extrusions. 
This invention positively meters food material through a plurality of dies. 
This assures that all flows remain open to all dies and rate predetermined 
by the capacity of the various metering means. This result is obtained 
regardless of the temperature of the material flow to any given die and 
completely overcomes the problems of all previous extrusion apparatus to 
multiple dies, where even a small temperature differential will always 
cause the catastrophic failure of total die blockages. 
In the prior art using pressure balancing to obtain uniform flow through 
multiple dies, the flow rates are dependent upon the sum of all pressure 
losses along all flow paths including the flow path through each die. This 
invention frees the die designer from the constraint of balancing the 
pressure losses in each flow path to the individual dies. This can greatly 
simplify the die design itself, which results in a die easier to 
manufacture and clean. As an alternative, a more complex die can now be 
used to obtain previously unattainable results. 
SUMMARY OF THE INVENTION 
This invention provides several embodiments of apparatus for extruding 
streams of food material through a plurality of dies using several 
metering means to prevent blockage of any individual die caused by 
material temperature differentials, and procedures for doing the same. In 
one embodiment a manifold, which provides a source of heated pressurized 
food material, feeds a plurality of pairs of gears having intermeshed 
portions which meter the material. These intermeshed portions of the gear 
pairs are interposed between the manifold and each die the intermeshed 
portion of each gear pair having an input receiving material from the 
manifold and an output feeding a separate die. Typically the gear pairs 
will all have identical displacements, however some pairs of gears can 
have different displacements by such means as having a different width or 
tooth depth to produce a different displacement, if desired. 
The gears are arranged such that a first half of the gears has a first 
shaft extending through them and a second half has a second shaft 
extending through them, with the first shaft having all the gears it 
extends through affixed to the shaft and the second shaft free-wheeling. 
This attachment of the first shaft forces all the gear pairs to rotate 
together in synchronism. This ensures that material will be metered by a 
gear pair through each die regardless of temperature differentials in the 
material creating differences in the material consistency. This results 
because the pressurized material introduced into the input duct acts upon 
all the intermeshed portions of all gear pairs and provides enough energy 
to them to cause them to rotate. All gears rotate in synchronism because 
of the first shaft attachment, and any local additional stiffness of 
material adjacent to any gear pair will not stop the rotation of the 
shaft. Since the rotation of the shaft rotates all gear pairs and the gear 
pairs provide positive displacement metering, material will continue to be 
fed to all dies regardless of localized viscosity changes. 
The gear pairs provide a metering function only, the pressure of the 
material leaving each gear pair being less than the pressure of the 
material entering each gear pair. The pressurized material need only 
provide enough energy for metering and need not provide enough energy for 
pumping. Further, the spacing between the gears in the gear pairs must be 
quite large for metering which is incompatible with pumping. Any food 
material with a cP of 100,000 or less can be metered by the energy from 
the pressurized food material alone. This includes marshmallow food which 
has a cP of around 100,000. A cp of around 100,000 results in a pressure 
drop of approximately 100 psi across a gear pair. 
If all the gear pairs have identical displacements the material stream into 
each die will be equal because of the shaft interconnection. If the gear 
pairs are unequal in displacement the material streams will also be 
unequal, but will have a volumetric ratio directly proportional to the 
gear pair displacements. 
Some food material is too viscous for the food pressure to provide adequate 
energy to operate the gear pairs in the manner described, since food 
material can have a cP of up to 20,000,000. As an example, using this 
arrangement material with a 1,000,000 cP would result in a pressure drop 
of greater than 150 psi. This is an unacceptably large pressure drop and 
would result in product shear damage. In addition, the large tolerances 
between the gears required for metering would permit food material to leak 
around the gears rather than turn them. These problems are overcome in a 
variation to this embodiment by having the shaft driven by a motor to 
provide additional energy. This driven arrangement has a maximum operating 
cP range of up to 20,000,000. Here again the pressurized material energy 
and motor energy need only be adequate for metering and not for pumping. 
The motor driving the common shaft can be provided with a controller. This 
controller can cause the motor to drive the shaft at a uniform rotation 
rate, resulting in uniform extrusions from each die with the ratio between 
them being determined by the gear pair displacements as before, or the 
controller can have selectable means to cause the shaft to rotate at 
varying predetermined rotation rates for special effects. This can 
including stopping the shaft for a predetermined period of time or even 
pulsing the shaft intermittently. Appropriate apparatus to obtain varying 
rotation rates can be accomplished by a number of mechanical or electrical 
apparatus and can readily be selected by those skilled in the art. 
Each gear pair meters the material and as a side effect also mixes it very 
well. This results because the gears meshing shears material caught in the 
teeth to provide an effective mixing action. This mixing action can be 
used to advantage by introducing an extrudable or even a pumpable 
supplemental material, under pressure which is substantially the same as 
that of the pressurized food material, into a gear pair input where the 
gear pair will mix it with the food material. This extrudable supplemental 
material can include such things as a liquid, a viscous solid, or a 
combination thereof. These examples are given as illustrations and not as 
a limitation, any material which can be pumped or extruded can be used as 
a supplemental material. 
This supplemental material can itself be or can contain a coloring agent, a 
flavoring agent, or any other agent or combination thereof which will 
modify a characteristic of the food material. Injected supplemental 
material which is a liquid will be mixed well with the food material by 
the action of the gear pair itself with no additional equipment being 
required. For extrudable material, static mixers, which are well known in 
the art, can be placed in the material stream between the meter and the 
die. This permits doing such things as extruding streams of food from 
different dies having different colors or flavors while using only one 
food material. 
The supplemental material can itself be displacement metered. When gears 
are used for metering, the gears of the supplemental material gear pair 
can be attached to the same shafts as the other gear pairs with its output 
flowing into the input of the gear pair metering the food material. Since 
this is supplemental material a smaller volumetric flow is required than 
that of the food material, but since the volumetric displacements of the 
two gear pairs can be made different, as described earlier, this is a 
feasible requirement. 
Other embodiments to the invention use different positive displacement 
metering of lobe impellers with either two or three lobes opposed to each 
other on two shafts as in the gear pairs. Four or more lobes could also be 
used for the impellers. Here too the energy for metering can be provided 
by the energy of the pressurized material or the energy can be 
supplemented by a motor. When lobe impellers are used the arrangement is 
almost identical to the gear pump arrangement where a plurality of lobe 
pumps feed a plurality of dies. Here however, the two shafts must both be 
attached to the opposed lobe pairs and the shafts must be synchronized by 
a gear pair since opposed lobe impellers are not self synchronizing. 
Another embodiment uses a plurality of vane impellers on a single shaft for 
metering food material to a plurality of dies. Here too the energy can be 
provided by the pressure of the material or the energy can also be 
supplemented by a motor. 
These apparatus and methods of using the same provides simple and effective 
means to completely overcome the previous problem of food material 
temperature differentials resulting in the catastrophic failure of a 
build-up of material completely blocking a die, because of the positive 
displacement action of the metering means. All of the metering means 
embodiments are arranged to be mounted in a split housing which is simply 
unbolted to remove and clean the metering apparatus. The simplicity of 
this apparatus is important because all equipment used for foodstuffs must 
be kept scrupulously clean. Cleaning complex machinery to the level 
required for foodstuffs is extremely difficult. The previous catastrophic 
build-up of food materials completely blocking the dies also required 
disassembly and cleaning every time a die was blocked with sanitation 
problems resulting from this repeated disassembly. 
In addition to the various positive displacement metering means provided, 
this apparatus and method provides the capability of extruding streams of 
material having different colors and/or flavors from a single food 
material.

DETAILED DESCRIPTIONS OF THE PREFERRED EMBODIMENTS 
An overview of multidie extrusion apparatus 50 is shown in FIG. 4. A hopper 
52 with counter-rotating augers 54 mounted along the bottom which are 
driven by motor 56, force food material placed in the hopper rightward 
through pipe 58 and into pump 60. Pump 60 is driven by motor 62. Pump 60 
pressurizes the material and forces it into heater 66 through pipe 68. A 
pressure sensor 127, mounted on the end of manifold 70, senses the 
internal pressure for feedback to motor 62 to obtain constant pressure on 
the material pumped into pipe 68. A heater and thermostat, not shown, 
heats the material within manifold 70 to a predetermined thermostatically 
controlled temperature. 
The heated pressurized material flows from heater 66 into manifold 70 
through pipe 68. Manifold 70 is adjacent to divided metering housing 73. 
Material 78 which was transported from manifold 70 through metering 
housing 73 thence to a number of dies 74, not shown in this figure located 
within die housing 76, is extruded as streams of such material to conveyor 
80, where they are carried away. This paths for the flow of material will 
be described later. 
Manifold 70, divided metering housing 73, die housing 76 and die holder 86 
are also shown in FIG. 5. Eight bolts 77 with attached nuts, not shown in 
this figure, extend through four upper holes 82 and four lower holes 84 in 
these parts hold them all together. 
Metering housing 73 is made up of an input portion 88 and an output portion 
90 which are essentially mirror images of each other. A set of seven holes 
92 which are aligned with each other provide a path for food material from 
manifold 70 through input housing portion 88. One hole is omitted because 
supplemental material rather than food material is fed to the metering 
means through a different hole, as will be described later. A second set 
of eight input duct holes 94 in input housing portion 88, aligned with 
holes 92, provide a path for food material through input housing portion 
90. A third set of eight output duct holes 95 aligned with holes 94 
provide a path to die housing 76. Dies 122, as shown in FIG. 6A, receive 
and extrude streams of material 78, shown in FIG. 4, received from output 
duct holes 95. 
A shaft 96 extends through and is affixed to eight upper gears 98 and a 
lower shaft 100 extends through and is free-wheeling to eight lower gears 
102. Each of the eight upper gears 98 are intermeshed with an opposite 
lower gear 102. This intermeshing of an upper gear 98 with a lower gear 
102 provides a positive displacement metering function. Input duct holes 
94 in input portion 88 and output duct holes 95 in output portion 90 of 
metering housing 73 are aligned with opposed intermeshed portions of gears 
98 and 102 which respectively receive and exhaust metered material. 
Each end 106 of gear frame 104 rotatably holds shafts 96 and 100. Spacers 
105 of gear frame 104, located between each opposed pair of gears 98 and 
102 also shown in FIG. 7, are shaped to closely fit within the cavity 
formed by recess 108 in input portion 88 and recess 110 in output portion 
90 of metering housing 73. Gaskets 112 mounted around each spacer 105 seal 
material within each gear pair. In addition, bearings and seals mounted 
within each seal on each spacer 105 around shafts 96 and 100, not shown, 
seal the shafts and permit the shafts to rotate. 
FIG. 6 shows metering housing 73, made up of input portion 88 and output 
portion 90, and die housing 76, all being held together by bolts 77 and 
attached nuts 79. An upper gear 98 is shown intermeshed with a lower gear 
102, with input duct hole 94 opposite output duct hole 95 and both 
opposite the intermeshed portion of the gears. Die 74 communicates with 
output duct hole 95 to receive material from the metering gears. Upper 
shaft 96 through upper gear 98 and lower shaft 100 through lower gear 102 
can be seen. FIG. 6A shows die opening 122 of one of the dies 76 which 
extrudes material. As also shown in FIG. 4, hole 114 extends through input 
housing portion 88 into the outermost input duct hole 92 with pipe 116 
conveying pressurized supplemental material from pressurized tank 117 into 
the hole. Pipe 116 injects supplemental material into the gear pair 
adjacent to frame end 106 to be mixed with food material. 
As shown in FIGS. 4 and 5, hole 118 through input housing portion into the 
input duct hole 94 second from end 106 has a pipe 120 conveying 
supplemental material into this hole from pressurized tank 117. This 
injects supplemental material only into the second pair of gear pairs to 
be metered, since the opposed manifold hole 92 is blocked. Hole 122 
opposite output duct hole 95 provides this metered supplemental material 
to pipe 124 to be conveyed to hole 126 into the adjacent inner input duct 
hole 94, which is third from outer end 106, to be mixed with food material 
from opposite input duct hole 94. 
Streams of material 78 are shown being extruded from dies 122 onto a moving 
conveyor belt 80 arranged to carry the extruded material away from all 
gear pairs, excepting only the second gear pair from the outer end as 
explained earlier. 
Motor 128 is connected to and drives upper shaft 96 in a direction which 
will meter material from input duct holes 94 through metering gears 98 and 
102 through output duct holes 95. Motor controller 130 will cause shaft 96 
to rotate at a constant speed unless modified by selectable control 
apparatus 132 which will cause the shaft to rotate at one of a number of 
preselected variable rates which change with time. Motor controller 130 
can be any one of a number of available motor controllers known in the 
art. In addition, control apparatus 132 providing a number of selectable 
variable changing rotation rates can be mechanical, electrical, computer 
generated or a combination thereof. Apparatus such as this is currently 
available in all these forms and one skilled in the art can readily select 
an appropriate control apparatus for this application. 
The positive displacement metering means described above is not the only 
positive displacement apparatus which can be used. FIG. 8 shows two lobe 
positive metering apparatus 136 comprised of opposed two lobe impellers 
138 and 140 affixed to shafts 142 and 144 respectively, which interleave 
to provide positive displacement metering. Shaft 142 replaces shaft 99 and 
shaft 144 replaces shaft 100 in FIG. 4, with housing 73 modified 
appropriately to contain eight two lobe positive displacement metering 
apparatus 136 in the same manner as the opposed upper gears 98 and lower 
gears 102. Synchronizing gears 99 and 101 are mounted on the end of shafts 
142 and 144 respectively with both shafts affixed to the respective two 
lobe impellers 138 and 140, because the two lobe impellers are not 
self-synchronizing. 
Shaft 142 can be driven by the pressurized material itself acting against 
the interleaved two lobe impellers 138 and 140, or it can be driven by 
motor 128, which can also be controlled as before for constant or varying 
rotation rates. 
FIG. 9 shows three lobe positive displacement metering apparatus 150, 
comprised of three lobe impellers 152 and 154 affixed to shafts 156 and 
158 respectively, which interleave to provide positive displacement 
metering. Shaft 156 replaces shaft 99 and shaft 158 replaces shaft 100 in 
FIG. 4, with housing 73 modified appropriately to contain eight three lobe 
positive displacement metering apparatus 150 in the same manner as the 
opposed upper gears 98 and lower gears 102. Here synchronizing gears 160 
and 162 are again mounted on the end of shafts 156 and 158 respectively 
with both shafts affixed to the respective three lobe impellers 152 and 
154, because the three lobe impellers are also not self synchronizing. 
Shaft 156 can be driven by the pressurized material acting against three 
lobe impellers 152 and 154 or it can be driven by motor 128, which can 
also be controlled as before for constant or varying rotation rates. 
Another positive displacement metering means is shown in FIG. 10 where 
positive displacement vane metering apparatus 166, mounted on shaft 170, 
has vane impeller 166 having individual vanes which slidably mate with 
receptacles and are urged outwardly therefrom by springs 168. Inlet 172 
and outlet 174 correspond to input duct holes 94 and output duct holes 95 
of metering housing 73, as shown in FIG. 5. Shaft 170 corresponds to upper 
shaft 96 of FIG. 6, however here only one shaft is used for the vane 
impellers. Housing 73 is modified appropriately to contain eight positive 
displacement vane metering apparatus 166 in the same manner as the opposed 
upper gears 98 and lower gears 102. Here synchronizing is not required 
because of only one shaft being used. 
Shaft 170 can be driven by the pressure of the material against the vane 
impellers 166, or it can be driven by motor 128, which can also be 
controlled as before for constant or varying rotation rates. 
This simple mechanical apparatus, which is easy to disassembly and clean, 
will extrude multiple streams of material with predetermined flow rates, 
depending upon the capacity of the gear pumps, with no possibility of 
unequal temperatures within the material mix causing any blockage of dies. 
In addition to continuous flow rates, non-uniform flow rates can be 
selected. Having the metering means arranged for easy cleaning is 
imperative in machinery for foodstuffs. Further, supplemental material can 
either be injected or metered into the food material at the input to the 
metering gears to provide extruded streams having different 
characteristics, such as color or flavor, using only a single food 
material. 
While this invention has been described with respect to a specific 
embodiment, this description is not intended to be construed in a limiting 
sense. Various modifications of the illustrative embodiment, as well as 
other embodiments of the invention, will be apparent to persons skilled in 
the art upon reference to this description. It is therefore contemplated 
that the appended claims will cover any such modifications or embodiments 
as fall within the true scope of the invention.