GB2051656A - Extrusion apparatus - Google Patents

Abstract

The invention relates to an auger type extrusion device for the production of starch based food products. The food products are partially cooked by compression and independent heat sources as they are transported by the auger (11) along a barrel (12) and through a forming die head (13). The barrel, die head, and auger are temperature-controlled by heating or cooling fluids fed through passages (38a, 45) in these components. <IMAGE>

Description

SPECIFICATION Extrusion devices for the production of food products This invention relates to extrusion devices for the production of starch based foods, and more particularly to extrusion devices of the type that are temperature controlled to partially cook the end product and control moisture content.

According to the invention, there is provided a farinaceous food product extrusion device comprising a auger having a continuous screw mounted within a barrel, a die head through which the food product is extruded, and means for controlling the temperature of the auger, barrel and die head whereby the temperature to which the food product is exposed along the length of the auger is controlled.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is an elevation of a cooking and forming extrusion device in accordance with the present invention, with the portion of a housing broken away for clarity in illustration; Figure 2 is a side elevation of a male die head of the extrusion device; Figure 3 is a front elevation of the male die head shown in Fig. 2; Figure 4 is an enlarged, vertical section of an auger and barrel assembly of the extrusion device; Figure 5 is an enlarged section taken on line 5-5 of Fig. 4; and Figure 6 is an enlarged side elevation view of a nose cone, secured to the end of the auger shown in Fig. 4, with portions of the auger and male die head shown in phantom.

There is shown in the drawings, an extrusion device 10 for production of food products in an intermediate half-product stage.

The device comprises an auger 11, with an input end 1 5 and an output end 18, rotatably mounted within a barrel 1 2 having three sections, 1 2a, 1 2b, and 1 2c, respectively.

The auger is adapted to transport and compress starchy or farinaceous grains through a die head 1 3. Suitable raw materials available for processing with the device include wheat, corn, rice, soy beam, potatoes and tapioca.

The extrudate, or half-product, formed at the output end 18 of the die head 1 3 has a carefully predetermined moisture content. To complete the preparation of the food product, the half-product is deep fried, for relatively short retention period, to cook and expand the half-product to produce a fried, puffed food product.

The production starts by supplying grains to a hopper 14 located at the input end 1 5 of the auger 11. A feed hole 1 6 is formed at a position vertically adjacent to the hopper 14 in the first section 1 2a of the barrel. Variable feed control of the hopper 14 is provided through conventional control means located on a base 48, which supports all components of the extrusion device 1 0. The base 48 can be of simple rectangular shape with cross member construction of, or any suitable conventional design and construction.

The auger 11 is so structured as to aid in final production of the half-product by first receiving raw material from the hopper 14 and feeding it along the barrel 1 2. As the raw material is moved down the barrel, increased pressures are applied as a result of a decrease in the cross-sectional area or space into which the material is moved. The sheer forces produced transform the raw material into a gelatinized stage. Provision is made for raising the temperature into the superheat range of water, as the raw material is transported along the barrel 12, in a manner to be discussed fully hereinafter. Gelatinization occurs through a second section 1 2b and into a third section 1 2c of the barrel. Finally, compression forces are reduced and cooling to a temperature below saturation takes place.At the output end 1 8 of the auger 11 the product is extruded through the die head 1 3 and cut into any desired length at the die head or at a remote position.

The end product desirably has a uniform moisture content of 9.5 to 10.5 percent water from an initial raw material moisture content of 25 to 30 percent. Deep frying of the extrudate at above 1 70 C. to about 21 0 C.

for about 10 to about 40 seconds expands the product volumetrically about 4 to about 10 times. Absorption of the frying oil results in about 20 to 35 percent oil content in the finished product. Suitable coating powders or flavor slurries can be added to produce the end product desired.

The auger 11 has both a tapered shank 21 and a continuous screw over a substantial portion of its length. The majority of the length of the auger 11 is a continuous Archimedian screw 20 contained within the three sectioned barrel 1 2. The flight of the screw 20 is configured so that rotation of the auger 11 moves raw material from the input end 1 5 toward the output end 1 8.

For purposes of increasing compression, and thereby adding heat to the product, the root diameter of the portion of the auger contained within the barrel 1 2 increases from the first section 1 2a of the barrel to a preselected position in the third section 1 2c. This root diameter is the diameter of the shank 21 of the auger at any given position along the continuous screw 20.

The barrel 1 2 contributes to the mechanical force applied to the product by defining a boundary through an interior surface 22 which maintains a constant diameter along the continuous screw 20 portion of the auger 11. As the shank or root diameter of the auger increases, the space between the shank 21 and the interior surface 22 of the barrel is decreased, while the pitch, or distance between adjacent flights of the continuous screw 20, remains constant, resulting in compression and the application of mechanical energy, which results in the production of heat, to the product being transported. This compression, or volumetric reduction in the raw material, should ideally be a ratio of between about 1.5 to 1 and about 4.5 to 1.It has been discovered that a ratio of between about 10 to 1 and about 20 to 1 between the length of the continuous screw portion of the auger 11 and the shank or root diameter of the auger is necessary to establish the proper contribution resulting from mechanical energy.

A portion of the auger 11 extends longitudinally away from the barrel 1 2 into a housing 23, which supports the auger 11. The housing is generally cylindrical and has disposed at either end a front cap 24 and a rear cap 25, the rear cap 25 being further from the barrel 1 2. The front end cap 24 fits around an integrally formed land 27 immediately adjacent to the barrel 1 2. The auger 11 extends away therefrom in an auger extension 29 or spline shaft. A drive spindle 28 is internally splined for driving engagement with the auger extension 29. The spindle 28 transmits rotational movement to the auger 11 from a motor 51 mounted to the base 48 through a chain drive 52. As with feed rate, the rotational speed of the motor 51 is variable through appropriate control means.This increased diameter from the spindle also increases the rigidity of the portion being driven by the motor 51 and thereby increases stability.

The spindle 28 protrudes through the rear cap 25 and is supported within the housing 23 by spaced bearings 32. Cap screws 34 connect both front and rear caps 24 and 25 to the housing 23. A pair of lock nuts 35 are threaded onto external threads of the spingle 28 to position the entire assembly. Rubber seals 26 can be positioned immediately adjacent to both caps 24 and 25 to protect the bearings 32.

A bore 38 is formed along the entire length of the auger 11. The bore 38 receives a coolant inlet pipe 38a which extends through the spindle 28 almost as far as the front end of the auger 11. Water or other coolant is supplied through the pipe 38a to the front end of the auger and then flows rearwardly between the outer surface of the pipe 38a and the internal surface of the auger 11 so that the auger is cooled along its entire length for more precise control of the temperature during the production process, and to further prevent excessive heating and resulting distortion and loss of tolerances. Variation of the rotational speed of the auger 11 also contributes to overall temperature providing additional temperature control. The pipe 38a may alternatively admit a heating medium, instead of a coolant.

The capability of having precise temperature control is necessary due to the conditions required for producing the extrudate half-product. In the first section 1 2a of the barrel, it is necessary to maintain a temperature just below the boiling point of water for example, approximately 80"C. In the second section 12b, the gelatinization and cooking section, additional heat into the superheat region, above the boiling point of water (for example 120"C. to 125"C.) is supplied to the processed material. The third section 1 2c is cooled slightly, to below saturation, or boiling point of water, temperature, (for example approximately 90"C).

With respect to the temperature control in the auger 11 through the pipe 38a and bore 38, coolant flows countercurrent to the direction the continuous screw 20 moves the raw material. As the heat increases along the length of the screw 20, as a result of the cooking process described above, the cooling capability is also increased by the fact that coolant stays at lower temperatures at the output end 18, picking up heat as it moves toward the input end 1 5. This helps control what temperatures occur within the auger 11 and barrel 12.

The output end 1 8 of the auger 11 terminates in a slightly converging conical nose cone 40. Raw material is moved between the nose cone 40 outer surface and the inner surface 22 of the barrel 1 2. Shaping of the passageway so provided can allow for some cooling through expansion. The nose cone 40 is threadably mounted onto the end of the auger 11 and directs the partially cooled extrudate to the die head 1 3.

The die head 1 3 includes two portions, a female head 41 and a male head 42. The female head 41 is externally threaded for engagement with internal threads on the end or third section 1 2c of the barrel 12. The nose cone 40 is retained in the female head 41 defining a relatively small space therebetween which can be either generally cylindrical configuration maintaining the constant diameter of the inner surface 22 of the barrel 1 2 or varied to thereby control cooling and expansion. A frusto-conical counterbore extends entirely through the female head 41 beginning longitudinally adjacent to the nose cone 40. Into the frusto-conical shape is inserted the male die head 42, held by the nose cone 40 or by conventional connection means into the female die head 41. A unique die head 1 3 is thereby formed at the interface between the male head 42 and the female head 41. The female head 41 presents a continuous smooth shape at the interface, while the male head 42 which is in a stationary position relative is the female head 41 is interspersed with longitudinal slots or flutes 44 through which the raw materials are forced by the auger 11.

As the raw material is extruded to form the half-product, additional temperature control is accomplished by cooling or heating of the die head 1 3. Cooling below superheat, the boiling point of water, is extremely critical as the product is extruded. Failure to cool below the superheat region would result in a substantial volumetric expansion and aeration because water in the material would flash to steam upon contact with air. Cooling at the die head 1 3 prevents superheating of the extrudate and loss of moisture. As the cooling takes place, expansion is greatly reduced. Later, in the deep frying stage of the cooking process, the energy retained within the extrudate in the form of retained moisture is released as the final product is produced by "puffing".Cooling of the die head 1 3 is accomplished by use of annular passages 45 into which coolant is admitted from a source (not shown) through couplings (not shown) on covers over the annular passages 45.

The barrel 1 2 is of generally cylindrical shape and retains the flighted screw of the auger 11. The feed hole 1 6 is located in the first section 1 2a and the die head 1 3 is mated to the output end 1 8 of the third section 1 2c.

The use of sections is disclosed as a preferred embodiment, for reasons that will be apparent; however, a single integral barrel would work as well. The interior surface 22 is dimensioned so that the screw 20 of the auger 11 is in minimal contact with the interior surface 22 by maintaining close dimensional tolerances. The interior surface 22 is splined with wedge shaped serrated teeth 50 about the circumference that act to impart a grinding action to the raw material that interferes with them upon rotation of the auger 11. As a result, mechanical energy is imparted and particle size is reduced to that necessary to pass between the screw 20 and the teeth 50.

The tapered shank 21 increasingly forces raw material to the periphery of the screw 20 and therefore into contact with the teeth 50.

Each of the sections of the barrel 1 2 are bolted together by use of cap screws 34 which join annular flanges 51 between the first and second and second and third sections. The first section 1 2a is joined in a like manner to the front cap 24 of the housing 23.

Annular passages 45, similar to those described in reference to the die head 13, are circumferentially disposed about each section separately. This arrangement permits independent control of heating and cooling for each stage of the production process. Thus in the second stage, where cooking to temperatures in excess of the boiling point of water are required, steam can be admitted through a coupling 53 in the cover over the annular passage 45. When cooling is required, as may be necessary in the third section 12c, water or other coolant can be admitted through the couplings 53. With a three sectioned barrel, as opposed to a single sectioned barrel, a greater degree of control over heating or cooling supplied to a given section can be achieved.An integral barrel would further conduct heat more readily along its length, than the sectioned barrel disclosed, although an integral barrel can be utilized with the spaced heating and cooling chambers.

The barrel 1 2 and contained auger 11 are supported by the base 48 in any conventional manner. The base 48 also forms the mounting for the motor 51 which in turn drives the spindle 28 through the chain drive 52. The motor is of variable speed for imparting differing mechanical forces to the raw material through the auger.

It will be apparent here, that in the auger, barrel and die head temperature control, appropriate temperature sensing devices can be strategically located along the length of the extruding device 10 to measure temperatures at critical locations previously enumerated.

Manual admission of coolant or heat can easily be effected through appropriate piping and valving from a steam or water source not shown. These instruments and controls are located on a cover 47 mounted to the base 48 which in turn supports the entire housing 23, auger 11, and containing barrel 1 2. Once the product is being produced at the desired quality and moisture content, automatic actuation of valving can be used to free the operator for other duties.

The product itself can have many different cross-sectional shapes. To one skilled in the art, many changes in die head construction are readily apparent to achieve this result.

Square, round and rectangular cross-sections are possible, as are virtually infinite dimensional changes.

It is also necessary, in using the extrusion device 10, to maintain a relatively high viscosity in the raw material. It has been found that raw materials having ten percent or less oil content can be extruded, while material with more than ten percent oil content generally will not extrude, or will extrude only with difficulty. For example, many corns have less than ten percent oil content and will therefore extrude in the device described. Peanuts, on the other hand, have a high oil content and cannot be extruded by this device because of the relatively low viscosity involved.

The extrusion device described, thus comprises an auger which transports and compresses the raw material through a gelantinization phase and through a cooking phase prior to being extruded and cut into a desired length. The auger is contained by a barrel which, like the auger, can be independently heated and cooled at selected positions along its length, to control the moisture content and expansion characteristics of the material processed. The end product is forced through a die head, also subject to temperature control, which governs the final shape of the product.

The final extruded product is in an unexpanded partially cooked or half-product form and can be stored for a length of time before being fully cooked or "puffed" by deep frying.

The food product is partially cooked by heat generated by the mechanical forces and the temperature control applied to the extrusion device prevents the product from releasing all of its energy and fully expanding at the die head.

The die head may easily be disassembled and cleaned.

Claims (22)

1. An extrusion device for the continuous production of partially cooked farinaceous food products, said device comprising an auger enclosed in a stationary barrel, said auger being rotatable to convey raw food material through the barrel and extrude the same through a forming die head, the auger being a continuous screw auger having a tapered shank diameter which increases along the length thereof in a direction towards the die head, means within the shank of said auger and about the circumference of said barrel and said die head for receiving controlled temperature fluids, for controlling the temperature of the barrel and auger.

2. An extrusion device according to claim 1, wherein said auger has a length to shank diameter ratio of between 10 to 1 and 20 to 1.

3. An extrusion device according to claim 1 or claim 2, wherein said barrel comprises three sections joined together at flanges, and an interior surface having wedge shaped serrated teeth around the circumference thereof and along the length of each said sections.

4. An extrusion device according to any one of claims 1 to 3, wherein the means within the auger for receiving controlled temperature fluid comprises a passage extending centrally through the auger to receive a fluid flow in a direction opposite to the feed direction of the continuous screw.

5. An extrusion device according to any one of claims 1 to 4, wherein the means on the barrel for receiving controlled temperature fluid comprises a plurality of passages disposed about the circumference of said barrel for receiving the fluid.

6. An extrusion device according to any one of claims 1 to 5, wherein the die head has a female portion with a frusto-conical opening and a male portion operatively received therein, a plurality of openings being defined about the interface between said male and female portions.

7. An extrusion device according to claim 6, wherein the means on the die head for receiving controlled temperature fluid comprises passages disposed about the outer circumference of said female portion for receiving the fluid.

8. A farinaceous food product extrusion device comprising a housing mounted on a base, said housing containing rotatably therein an auger extending longitudinally away therefrom in a hollow tubular barrel of generally cylindrical shape connected to said housing and rotatably supporting said auger therein, said auger comprising a hollow tubular shank and a continuous screw along the portion of said auger retained by said barrel, a hopper adjacent to said continuous screw of said auger and longitudinally adjacent to said housing to feed food products to said auger through a hole in said barrel, a die head connected to the barrel at the output end of said auger, said die head having a generally cylindrical female portion with a conical opening wherein a male portion is matingly received, the interface therebetween having a plurality of openings, the hollow shank of the auger being arranged to receive coolant or a heating medium, passage means disposed about the exterior circumference of said barrel and along the length thereof, and passage means disposed about the circumference of the female portion of said die head, said passage means being arranged to receive coolant or a heating medium.

9. An extrusion device according to claim 8, wherein the auger has a length to diameter of between 10 to 1 and 20 to 1 and said shank diameter increases from the input end adjacent the hopper along the length of said auger to the output end.

10. An extrusion device according to claim 8 or claim 9, wherein the barrel includes three sections connected together through flanges therebetween and said barrel has an interior surface retaining said auger, including wedge shaped serrated teeth disposed about the inner circumference thereof.

11. A farinaceous food product extrusion device comprising an auger having a continuous screw mounted within a barrel, a die head through which the food product is extruded, and means for controlling the temperature of the auger, barrel and die head whereby the temperature to which the food product is exposed along the length of the auger is controlled.

1 2. An extrusion device according to claim 11, wherein the auger has a length to shank diameter ratio of between 10 to 1 and 20 to 1.

1 3. An extrusion device according to claim 11 or claim 12, wherein the barrel is constructed of a plurality of sections bolted together through flanges.

14. An extrusion device according to any one of claims 11 to 13, wherein the barrel has wedge-shaped serrated teeth disposed about the interior circumference thereof.

1 5. An extrusion device according to any one of claims 11 to 14, wherein the auger is hollow along the length of its shank.

16. An extrusion device according to claim 1 5, wherein the means for controlling the temperature of the auger comprises means for admitting coolant or a heating medium to the hollow shank of said auger from the end adjacent to the die head.

1 7. An extrusion device according to any one of claims 11 to 16, wherein the means for controlling the temperature of the barrel comprises passage means around the circumference of said barrel to receive coolant or a heating medium.

1 8. An extrusion device according to any one of claims 11 to 17, wherein the means for controlling the temperature of the die head comprises passage means in the die head to receive coolant or a heating medium.

1 9. An extrusion device for the continuous production of partially cooked extruded farinaceous food products, comprising a base, a stationary auger barrel supported on said base, a hopper positioned above said barrel and connected therewith for feeding raw farinaceous food product material to the inlet end of said auger barrel, a hollow shank auger rotatably supported in said barrel, said auger having a tapered shank diameter with said diameter increasing along the length thereof from the inlet end of said barrel to the outlet end of said barrel, said auger having a continuous Archimedian screw flight thereon extending from the inlet end to the outlet end, drive means on said base, means drivingly connecting said drive means to said auger to rotate said auger in said auger barrel, means within the hollow shank of said auger for controlling the temperature of said auger, means surrounding the circumference of said barrel for controlling the temperature of said barrel and the auger contained therein, and an extrusion die head at the outlet end of said barrel in juxtaposition with the end of said auger whereby farinaceous material fed to said auger barrel and auger is ground and partially cooked within said auger barrel as said auger rotates therein and extruded from said forming die head.

20. An extrusion device according to claim 19, wherein said die head comprises an outer sleeve having an exteriorly threaded end adapted for threaded engagement with the outlet end of said barrel, said sleeve having an interior frusto-conical bore therein tapering inwardly from the inlet end of said heat to the outlet end thereof, and a fluted frusto-conical insert received within said bore and adapted to define therewith a plurality of outlet die openings.

21. An extrusion device for the continuous production of partially cooked extruded farinaceous food products, comprising a base, a stationary auger barrel supported on said base, a hopper positioned above said barrel and connected therewith for feeding raw farinaceous food product material to the inlet end of said auger barrel, a hollow shank auger rotatably supported in said barrel, said auger having a tapered shank diameter with said diameter increasing along the length thereof from the inlet end of said barrel to the outlet end of said barrel, said auger having a continuous Archimedian screw flight thereon extending from the inlet end to the outlet end, drive means on said base, means drivingly connecting said drive means to said auger to rotate said auger in said auger barrel, a temperature control fluid tube within the hollow shank of said auger for directing temperature control fluid into said auger in countercurrent flow relative to said farinaceous food product material to control the temperature of said auger, a plurality of fluid chambers surrounding the circumference of said barrel for receiving temperature control fluid to control the temperature of said barrel and the auger contained therein, and an extrusion die head at the outlet end of said barrel in juxtaposition with the end of said auger and comprising an outer sleeve having an exteriorly threaded end adapted for threaded engagement with the outlet end of said barrel, said sleeve having an interior frusto-conical bore therein tapering inwardly from the inlet end of said head to the outlet end thereof, and a fluted frusto-conical insert received within said bore and adapted to define therewith a plurality of outlet die openings, whereby farinaceous material fed to said auger barrel and auger is ground and partially cooked within said auger barrel as said auger rotates therein and extruded from said forming die head.

22. An extrusion device substantially as hereinbefore described with reference to the accompanying diagrammatic drawings.