SUMMARY OF THE INVENTION The present invention will be described with reference to agricultural crops. However, the apparatus and method of the present invention may be used to dry any type of suitable material and no limitation is intended thereby.

Many agricultural crops are harvested, dried and stored for future use. In particular, lucerne and other forage crops for cattle and the like are treated in this way to produce hay or dry silage. Traditionally crops are harvested and left to dry in the sun. However, the crops are subject to spoilage if it rains. A further disadvantage of this method is that it can take a considerable period of time before the crop is dry enough to be stored or sold. Also any irrigation or fertilisation of the growing crop must be postponed until the dried crop is removed from the field.

Previous attempts to overcome these problems include drying the harvested crop in a large microwave oven. This is very expensive and normally not economically viable. This process is also a batch process and the crop must be loaded and unloaded from the oven after each drying stage. Another method for drying crops injects hot air into a mound of undried crop. Difficulties associated with this method is non-uniform heating and drying.

It is also known to dry materials in chambers through which the material to be dried is conveyed between an inlet and an outlet. Generally a strong flow of warm air is passed through the chamber. Such dryers are typically used for drying products such as tobacco, tea and also fodder. The material dries as it passes through

the chamber from the inlet to the outlet. The chamber may include an auger mounted on a central shaft for moving the material to be dried along the chamber. Alternatively or in addition to the auger, the chamber may be rotatable and is inclined downwardly towards the outlet. A disadvantage with such drying chambers is that in order for the residence time in the chamber to be sufficient to dry the material, the chamber must typically have a minimum length. Thus, these known types of dryers are generally large, fixed constructions. This makes them unsuitable and uneconomical for small scale operations. It is also not economically viable to construct such driers for onsite operations.

In order for these driers to be able to satisfactorily dry a product, the chambers must be sufficiently heated. A further disadvantage of these driers is the necessity to provide heating means on a large scale. Typically the driers include large and complicated fan and heater assemblies for providing a strong and constant source of warm air throughout the chamber.

It is therefore an object of the present invention to provide a drier which may overcome at least some of the above disadvantages or provide the public with a useful or commercial choice.

According to a first broad form of the invention there is provided a drier including; a drum mounted for rotation, the drum having a main body and a forward chamber through which a material to be dried is introduced into the drum; a helical auger located inside the drum body; a helical auger located inside the chamber; means for introducing a gaseous drying agent into the drum body; whereby the material to be dried is introduced into the chamber and conveyed towards an end of the drum remote from the chamber when the drum rotates in one direction and the material is conveyed towards the chamber

and expelled from the chamber when the drum is rotated in the other direction.

According to a second broad form of the invention there is provided a method for drying a material, which method comprises; rotating the drum of the drier described in the first broad form in one direction ; loading the material to be dried into the chamber of the drier such that the material is conveyed towards an end of the drum remote from the chamber and introducing a gaseous drying agent into the interior of the main body of the drum and rotating the drum in the other direction to convey the dried material towards and out of the chamber.

The drier of the present invention may be used to dry any suitable material. The drier is especially suited to dry forage crops including those used for silage such as lucerene and forage sorghum. The drier is also suitable for tobacco, herbs, and food stuffs.

The drier includes a drum which is mounted for rotation. The drum may be rotated by any suitable means.

The drum may have perforated walls through which in use the gaseous drying agent and any water vapour may pass.

Alternatively other outlet means may be provided for the gases. The outlet for air and water vapour may be the same as the inlet through which the material to be dried is introduced. The chamber and/or drum may have at least part of their respective perimeters formed from a mesh.

The size of the mesh may be varied as desired according to flow rates, the material to be dried and the like.

The drum has a forward chamber through which a material to be dried is introduced into the drum when the drum is rotated in one direction and through which the dried material is unloaded when the drum is rotated in the other direction.

The main body of the drum has a helical auger located inside it. The helical auger assists in conveying the material for drying away from the chamber and into the

drum during rotation in one direction and conveys the material towards the chamber when rotation is in the other direction. The main body of the drum may have one or more further augers located inside it. These further augers may also facilitate movement of the material through the drum body. The or each auger may also assist in mixing and dispersing of the material inside the drum body. The number of augers may be varied according to the type of material to be dried. The pitch, length and width of the auger may also be varied as desired. For example, a drum having four augers may be more suitable for a heavier material than a drum having two augers. If desired the drum may include further mixing means such as mixing blades or the like for mixing the material during drying.

The forward chamber also has a helical auger.

This auger typically moderates the rate of flow of the material through and out of the chamber during loading and unloading of the drum. The chamber auger may be an extension of an auger of the drum body. Alternatively the chamber auger is separate from the auger of the drum body.

Typically the chamber auger has a shorter pitch and a more acute pitch angle than the or each auger of the main body.

Preferably the auger in the chamber has a wider blade than the or each auger of the drum body. The blade being that part of the auger which contacts and pushes against the crop during rotation of the drum. The wider blade may also assist in regulating the flow of material within the chamber. Typically the chamber auger has a blade 200 mm wide and the blade width of the or each auger of the main body is 50 mm.

The drier has means for introducing a gaseous drying agent into the interior of the drum. Any type of gaseous drying agent may be used and is typically hot air.

The gas may be introduced into the drum by any suitable means and comprise a series of perforated conduits. The drying agent passes from the conduits through the perforations and into the drum. The conduits are typically located at positions within the drum such that

the drying agent is distributed substantially evenly throughout the interior of the drum such that the particles to be dried experience substantially the same drying environment throughout the drum body.

According to a third broad form of the invention there is provided a drier for an agricultural crop having; a drum mounted for rotation, the drum having a main body and a forward chamber through which crop is introduced into the drum; a helical auger located inside the drum body; a helical auger located inside the chamber; means within the drum body for distributing a gaseous drying agent in a substantially uniform manner inside the drum body; whereby crop is introduced into the chamber and conveyed towards an end of the drum remote from the chamber when the drum rotates in one direction and crop is conveyed towards the chamber and expelled from the chamber when the drum is rotated in the other direction.

In one form of the invention the or each auger in the main body of the drum is hollow and perforated. The drying agent is delivered to the interior of the drum through the or each auger. Alternatively separate conduits may be provided for distributing the heating agent. Preferably these separate conduits also assist in mixing of the crop inside the drum. The perforated conduits may also be provided in addition to the perforated augers if desired. The combination of perforated and/or nonperforated augers and perforated conduits may be varied depending on the type of material to be dried.

In an especially preferred embodiment, the gaseous drying agent is blown upwardly into the drum from a lower portion of the drum walls. When the gas is introduced into the lower portion of the drum, it is especially preferred that the auger and/or any additional blades or vanes in the drum lifts the material away from the drum floor during rotation of the drum. Such lifting

in combination with the upward flow of gas facilitates drying. Preferably introduction of the gas occurs at specific time intervals timed to correspond to the lifting of the material.

Thus according to a further embodiment of the present invention there is provided a drier, the drier having a drum mounted for rotation, means for introducing a gaseous drying agent into a lower section of the drum such that there is an upward flow of drying agent and means for lifting material being dried away from the lower section of the drum when the drum is rotated.

The means for lifting the material as it dries may be in the form of vanes or paddles mounted on the drum walls. Alternatively, or in addition to, the lifting means may be an auger. The auger vanes or paddles may have folds, projections or the like which can scoop the material upwardly during rotation of the drum.

The drum of the further embodiment is preferably mounted for rotation in two directions, but this is not necessary. The drum may be loaded and unloaded by means other than provision of a forward loading chamber as described in the first broad form of the invention. For example the material may be loaded and unloaded by hatches located in the walls of the drum.

In a preferred form of the invention the drum is mounted for rotation in both directions and includes one or more helical augers. The blades of auger (s) are tpyically folded in such a manner such that when the drum is rotated in one direction the major action of the auger is to lift the material being dried in a uniform manner rather than transfer the material laterally. However, when the drum is rotated in the reverse direction, the auger blades are shaped such that the major movement of the material is towards the material outlet instead of a lifting action. In this way, the material can be dried for any desired residence time without the excess material being conveyed to the end of the drum. When drying is complete and the drum rotation is reversed, the material

can be emptied from the drum.

In use, a material to be dried such as a harvested crop is fed into the drum. The crop may be fed manually or automatically by using a conveyor or the like.

Preferably the crop is crushed or squeezed prior to the loading to remove at least part of the moisture.

In the drier of the first embodiment of the invention and the drum rotates in the first or loading direction, loading is assisted by the helical auger located in the chamber which moves the crop from the front to the rear of the chamber and into the main body of the drum. The or each auger in the main body of the drum then conveys the material towards the end of the drum remote from the chamber. The or each auger may also contribute to mixing and distributing the material within the drum.

The material is mixed and distributed throughout the body of the drum when the drum is rotating. The drying agent such as air is introduced into the drum so as to dry the material. When the material is dried to the desired amount the drum is rotated in the reverse direction such that the material is moved from the drum into the chamber for unloading through the chamber.

The drier of the present invention is preferably constructed so it can be mounted onto a truck or trailer.

In this way the drier can be used on site to dry crops immediately they have been harvested. When the drum is full the drier and dried crop may then by driven away the site for off-loading.

By way of example only the present invention will be described with reference to the accompanying figures in which Figure 1 is an isometric open view of a preferred drier of the present invention; Figure 2 is an isometric open view of a further preferred drier of the present invention; Figure 3 is an isometric open view of a further preferred drier of the present invention; Figure 4 is a schematic view of a drier of the

present invention together with a hot air source; Figure 5 is a schematic view of a drier of the present invention in operation; Figure 6 is a schematic side view of a further preferred drier of the present invention; Figure 7 is a cross-sectional view of the drier of Figure 6; Figures 7a, b and c are details of auger blades of the drier; Figure 8 is a sectional end view of the drum portion of the drier illustrated in Figures 6 and 7.

Figure 1 illustrates a drier 11 having a drum with a main body 12 and a frusta-conical forward chamber 13. The drier 11 is particularly suitable for drying silage crops. The chamber 13 has an opening 14 through which the crop is loaded and unloaded. The chamber has a helical auger 15. The drum 12 has a shaft 16 extending longitudinally from the center of the rear wall 18 of the drum body. The shaft terminates where the chamber joins the drum body. The shaft has an inlet 17 at the rear end for hot air. Four arms 19 to 22 extend radially from the rear end of the shaft and terminate at the circumferential wall of the drum. Four further arms 23 to 26 extend radially from the opposite end of the shaft. The arms are orientated so that each arm at one end of the shaft aligns with a corresponding arm at the opposite end of the shaft.

Each arm has a helical auger 27,28,29,30 extending from it. Each auger terminates at a respective arm at the opposite end of the shaft. The shaft, arms, and augers are all in fluid communication. The heating agent, typically hot air, flows into shaft 16 through inlet 17 and toward the chamber end of the drum.

The heating agent enters the arms 23 to 26 and flows towards the rear of the drum along augers 27-30.

The augers are perforated to allow the hot air to flow into the interior of the drum in an even and uniform manner.

Figure 2 illustrates a drier 31 similar to that illustrated in Figure 1 except that only two arms 32 and 33 have augers 34 and 35 extending therefrom.

Figure 3 illustrates a drier 41 which is similar to that illustrated in Figure 2 expect that there is only one helical auger 42. This auger is not perforated and hot air does not flow through it. Four bars 45 to 48 join respective aligning arms 43 to 44,49 to 50,51 to 52,53 to 54. These bars lie adjacent the circumferential wall 55 of the drum. The bars are hollow and perforated. Hot air enters the interior of the drum through the perforations in the bars.

Figure 4 schematically illustrates a drier 60 together with a motor/fan assembly 61. The motor/fan assembly supplies the hot air heating agent to the drier.

The assembly 61 has a motor 62 and a hydraulic motor 63.

The motor 62 is typically a portable air-cooled engine.

The air which is heated during cooling of the engine is used as the drying agent. If necessary, further heating of the air may be provided by means of a gas burner or the like. The hydraulic motor operates a shaft 64 upon which two sets 65,66 of fan blades are mounted. Hot air generated by motor 62 is forced by the fans into a duct 67. The duct joins the inlet 17 of the shaft of the drier. The direction of the air flow in the drum is schematically illustrated by arrows 68. The motor/fan assembly and duct are fully enclosed.

Figure 5 schematically illustrates a drier 69 in use. The drier is mounted onto a truck (not illustrated).

The harvested crop 70 is fed into a hopper 71. Two opposing spring loaded rollers 72,73 are located rear the outlet 74 of the hopper. The rollers crush the crop so as to remove excess moisture. The rollers also assist in aligning the crop on the conveyor belt. A conveyor belt 75 transfers the partially dry crop to the inlet 14 of the drier 69. A hydraulic ram 76 operates to lift and lower the belt away from drier 69. When the crop has been loaded, the belt 75 is lowered. The drier can be driven

to an unloading point. The crop is unloaded by rotating the drum in the unloading direction.

Figure 6 illustrates a further preferred drier 80 of the present invention. The drier 80 has a conical forward chamber 81 and a drum 82. The drum 82 has a number of hatch doors 83. The hatch doors allow access to the interior of the drum 82 for maintenance. The drum 82 is mounted on a frame member 84. The frame member 84 is pivotable about pivot point 85 which enables the inclination of the drum to be varied. In use the longitudinal axis of the drum is typically about 10° from the horizontal. In this position, crop 86 is prevented from falling from the opening 87 of conical chamber 81. At the end of the drum 82 remote from the conical chamber 83 is an arrangement 87 for supplying hot air to the drum 82.

The air supply includes a gas heater 90 fluidly connected to duct 91. At the rear of the assembly is a housing 92 which contains a fan 93 (illustrated in Figure 7). The drier 80 further includes a drive assembly 94 for rotating drum 82 in either an anti-clockwise or clockwise direction.

Figure 7 is a cross-sectional view of the drier of Figure 6, except that in this view, the drum 82 is illustrated in the horizontal position. Conical chamber 81 has a helical auger 95. Drum 82 also has an auger 96 which is separate from auger 95. The pitch angle of the drum auger 96 is greater than that of cone auger 95. The pitch angle influences the speed at which the rotating auger conveys the crop. The smaller pitch angle of the cone auger 95 enables crop to be conveyed through the cone faster than the rate at which the drum auger 96 conveys crops. The cone auger facilitates pitch angle loading and unloading through the cone. The cone auger has an effective pitch angle of about 30°. This angle may be varied between about 25 to 35° if it is desired to vary the cone feed rate. The pitch angle of the drum auger 95 is typically about 38.5°, but again may be varied with

angles between about 30-45° being suitable.

The flow of air through the drier is illustrated by arrows. A fan 93 forces air past heater tube 91 and the heated air enters transition chamber 98. The chamber has an upper downwardly sloping wall 99 which prevents upwards air flow and directs the air flow as indicated.

The air is shown entering a chamber 100. The chamber 100 extends along the lower potion of the drum 82.

Perforations of holes 101 allow the air to pass into the lower portion of the drum 82. The air passes upwardly through crop in the drum 82 and escapes through the mouth 87 of conical chamber 81.

The drum auger 96 has a number of vanes 102 with a fold line 103 as shown in Figures 7a to c. Figures 7b and c are side and end views of the folded vane. This fold allows the auger to scoop and lift the crop when the drum is rotated during the drying operation. Typically the crop is lifted towards the upper third of the drum.

Air is blown into the crops during the lifting motion. As the crop drops, moist air is exhausted through conical chamber 81 as shown by the arrows. The inflow of air from chamber 100 into drum 83 is not constant and is timed to coincide with the lifting action of the folded auger vanes. This allows aeration of the crop to be optimised which facilitates drying. This timing may be accomplished by having a plurality of discrete chambers 100 as illustrated in Figure 8. There are eight chambers radiating from central portion 102. As the drum rotates, the open ends 103 of chambers 100 periodically align with the outlet from chamber 98.

The drier 80 is also provided with scales 104 for weighing the crop therein. The weight may enable the drying process to be monitored. The scales also enable the dried weight of the crop to be calculated. The drying process may also be monitored by the use of a moisture or humidity meter located near the mouth of the conical chamber 81. The speed of rotation, temperature and

residence time of the crop may be varied according to variables including type and amount of crop when the crop has been dried, the rotation of the drum is reversed. In the reverse direction, the folded vanes of the drum auger 95 no longer lifts the crop, but instead conveys the crop towards conical chamber 81 for unloading.

When the drier is used to dry crops, the harvested and dried crop may be removed from the field immediately after harvesting. This allows the growing crop to be immediately irrigated, fertilized or grazed.

The crop may also be dried, packaged or sold immediately.

No crop is left lying in the field where it may be subjected to rain damage.

It should be appreciated that various other changes and modifications may be made to the embodiment described above without departing from the spirit and scope of the invention.