A DRIER FOR GRAIN AND GRANULAR MATERIALS IN GENERAL

Abstract: A drier for grains and similar material comprises a drying chamber (10) and a first vertical screw conveyor (15) associated with the drying chamber for picking up material from the lower portion (10b) of the chamber (10) and carrying it to the upper portion of the chamber. The vertical screw conveyor (15) is arranged outside the drying chamber (10) and is coupled at its lower end to a second horizontal screw conveyor (14) operative between an output opening (11) provided in the lower portion (10b) of the chamber (10) and the vertical conveyor (15). A mixer device with radial blades (21) is mounted in the lower portion of the drying chamber, immediately above the output opening (11) to provide both for mixing of the material and for directing it forcedly through the output opening (11) into the second horizontal conveyor (14).

Description: A DRIER FOR GRAIN AND GRANULAR MATERIALS IN GENERAL Technical field The present invention relates to a drier for grain and granular materials in general . Grain is normally dried upon harvesting to prevent it from deteriorating; the present invention is for application particularly but not exclusively in the field of mobile driers which are positioned in the vicinity of the grain- harvesting areas in order to dry the grain on the spot within short periods of time. Background art A conventional drier of the type which is the subject of the invention comprises a vertical, cylindrical drying chamber, a heating unit for producing hot air, and a fan which admits the hot air to the drying chamber and circulates it to promote evaporation of the moisture contained in the grain being dried. A screw conveyor is disposed along the central vertical axis of the drying chamber into which the bulk grain is loaded. In use, the moist material is picked up from the base by the screw conveyor and is carried to the top of the screw, so that the material is caused to circulate inside the drying chamber in order to bring about movements of material which accelerate the drying process and render it uniform. Screw conveyors disposed vertically inside the cylindrical drying chamber have some disadvantages, one of which is connected with their bulk which limits the useful volume of the drying chamber. Moreover, all of the maintenance operations on the conveyor have to be performed inside the chamber, and this may be particularly complicated or even impossible when the drier is filled with grain. Moreover, the central screw tends to "reject" the moist grain dropped in, rendering the transportation-rate of the conveyor non-homogeneous . This also leads to a lengthening of the drying time and a to relatively poor performance of the plant as a whole. Disclosure of the Invention The object of the present invention is to provide an improved, high-performance drier which can make maximum use of the volume of its drying chamber. This object is achieved, according to the present invention by a drier having the characteristics set forth in Claim 1. Another object of the present invention is to provide a drier which improves the circulation and mixing of the material and prevents stagnation thereof in order to achieve, within short periods of time, a high and homogeneous degree of drying of the bulk grain to be dried. This object is achieved, according to the present invention, by a drier having the characteristics recited in Claim 2. A further object of the present invention is to propose a drier in which the loading of the moist material to be dried is also improved. This object is achieved, also according to the present invention, by a direr having the characteristics set forth in Claim 3. Further important characteristics are recited in the further dependent claims . Brief description of drawings Further characteristics and advantages of the invention will become clearer from the detailed description of an embodiment thereof given with reference to the appended drawings, provided by way of non-limiting example, in which: Figure 1 is a partially-sectioned, side elevational view of a drier according to the present invention, and Figure 2 is a partially-sectioned, perspective view of a detail of the drier of Figure 1. Best mode of carrying out the invention With reference to Figure 1, a mobile drier according to the present invention, for grain and other granular materials, is generally indicated 1. The drier 1 comprises a drying chamber, generally indicated 10, which is composed of a cylindrical, main, upper portion 10a and a frustoconical, hopper-like lower portion 10b which terminates in an output opening 11 closable by a horizontal sliding shutter plate 11a. The chamber 10 is mounted on wheels 12 so that the drier is mobile and can be transported to the vicinity of the harvesting location where drying is performed. Beneath the output opening 11, and hence outside the chamber 10, there is a horizontal screw conveyor, generally indicated 14. The horizontal conveyor 14 comprises an internal screw in which it is possible to distinguish a first, central portion 14a oriented so as to transport the material coming from the output opening 11 in a radially outward direction (as indicated by the arrow A) towards the periphery of the chamber, where the screw conveyor 14 is coupled to a vertical screw conveyor 15. The vertical conveyor 15 extends parallel to the central vertical axis X of the chamber and extends vertically from the base of the chamber to a point situated above the top of the chamber 10. At the top of the vertical screw conveyor 15 there is an inclined outlet duct 19 along which the material which comes out of the vertical conveyor 15 can fall into the chamber 10 or to the exterior during the discharge (emptying) of the drier. The horizontal screw conveyor 14 is extended externally and radially beyond the point of coupling with the vertical conveyor 15, forming a second portion or outer appendage 14b; in this second portion, the spirals of the screw 14 are oriented in opposition to those of the first, central portion, that is, so as to transport material from the exterior towards the point of coupling with the vertical screw conveyor (as indicated by the arrow B in Figure 1) . The opposed portions 14a and 14b are connected by a radial blade 24 for urging the material arriving either from the right or from the left into a chamber 23 which contains the lower portion or foot of the vertical screw 15. A power take-off, by means of which the horizontal screw conveyor 14 can be rotated by being connected, by means of a Cardan shaft, to a motor, for example, the power take-off shaft of an agricultural tractor, is indicated 16. The outer appendage 14b of the horizontal screw conveyor is arranged for the loading of the moist material to be dried by means of a loading conveyor, indicated 17, which is driven by a transmission system 18 connected to the screw conveyor 14, and hence to the power take-off 16; the loading conveyor 17, which is preferably also of the screw type, is arranged for receiving the as yet moist grain harvested and transporting it in the direction indicated by the arrow C, towards an end 17a which is disposed above the outer appendage 14b of the horizontal screw conveyor. The loading conveyor 17 can advantageously be tilted to adopt an inactive, vertical position (not shown) for operations during which it is not required to operate, for example, for transportation or during the drying process upon completion of the loading. A reduction gear for taking the drive from the horizontal screw 14 and transferring it to the vertical screw 15 is indicated 20. In the lower portion of the drying chamber, immediately above the output opening 11, there is a mixer with radial blades 21 which are spoon-shaped so as to provide both for mixing of the grain and for directing it from the exterior towards the interior in a substantially radial direction. It will be appreciated that, since the mixer 21 is located in the base of the hopper 10b, it has relatively short blades, leading to low torques transmitted. The mixer can collect all of the material falling down in order to supply it to the output opening. The optional presence of conventional auxiliary scrapers (not shown) , rotated about the axis of the mixer 21 and passing close to the wall of the hopper 10b, is also envisaged. A heating unit is also provided for producing hot air and admitting it to the drying chamber to promote evaporation of the moisture contained in the grain. The drier according to the present invention operates as follows . First of all, the moist material is loaded onto the loading conveyor 17 where it reaches the end 17a and falls by gravity into the outer appendage 14b of the horizontal screw. A box-like container 22 surrounds the end 17a laterally in order to direct the moist grain into the appendage 14b, preventing it from being dispersed. By virtue of the orientation of the horizontal screw in the second, outer portion 14b, the material admitted to the horizontal screw from the exterior is transported towards the point of coupling with the vertical screw conveyor 15, where it is picked up by this vertical screw and lifted to the top thereof in order then to be discharged through the duct 19 and to fall into the upper portion of the drying chamber 10. The grain inside the chamber 10 continues gradually downwards until it emerges from the lower opening 11, where it is loaded onto the central portion 14a of the horizontal screw conveyor 14 and is thus transported towards the vertical conveyor 15. The forced supply by means of the vertical screw 15 prevents stagnation or partial rejection of the grain during the initial drying stage (moist grain) and a consequent reduction in the recirculation rate. The mixing and recirculation cycle then continues normally by means of the vertical conveyor 15, the upper outlet duct 19, the drying chamber 10, and the portion 14a of the horizontal screw conveyor . As can be appreciated, the drier according to the present invention enables maximum use to be made of the capacity of the drying chamber, considerably increasing the performance of the plant and thus reducing running costs . Moreover, there are no points of stagnation of the material and/or variations in the recirculation rate so that the drying which is achieved is homogeneous throughout the bulk material in circulation; moreover, the drying times necessary to achieve, throughout the bulk material, the degree of humidity required for optimal preservation of the material are reduced. The drier of the present invention puts all of the material emerging from the output opening 11 into forced circulation, transporting it forcedly in the vertical screw conveyor 15. The mixer 21 is positioned and shaped in a manner such as also to force the grain which is disposed close to the wall of the drier to slide downwards; the material disposed further towards the interior, which is more greatly affected by the drying hot-air flow is thus mixed quickly and uniformly with that situated in the peripheral portion of the chamber. It will also be appreciated that the mixer 21, which works in the bottom of the frustoconical portion of the drying chamber with short blades, is subject to a very low resisting torque, even in the presence of very moist grain. In contrast, in conventional driers, in which the vertical screw conveyor is immersed in the bottom of the drying chamber, the blade mixers also have to shift the material from the conical wall of the drying chamber in order to bring the material uniformly towards the bottom and therefore include long blades which encounter a large resisting torque. The drier of the invention advantageously works with an approximately constant flow-rate with both moist and dry grain, whereas in conventional driers, the flow-rate is slower when the grain is particularly moist; an improved exchange of heat between the grain and the hot air admitted to the drying chamber is thus achieved so that all of the available heat is advantageously utilized, even in the initial stages of the drying cycle.

Claims: CLAIMS 1. A drier for grain and similar materials, comprising: - a drying chamber (10) , and - a first vertical screw conveyor means (15) associated with the drying chamber (10) for picking up material from the lower portion (10b) of the chamber and carrying it to the upper portion (10a) of the chamber, said vertical screw conveyor means (15) being disposed outside the drying chamber (10) and being coupled at its lower end to a substantially horizontal second conveyor means (14) operative between an output opening (11) provided in the lower portion (10b) of the chamber and the first vertical screw conveyor means (15) , characterized in comprising a mixer device with radial blades (21) mounted in the lower portion (10b) of the drying chamber (10) , immediately above the output opening (11) to provide both for mixing of the material and for directing it forcedly through the output opening (11) into the second horizontal conveyor means (14) . 2. A drier according to Claim 1, characterized in that the second horizontal conveyor means (14) is of the screw type and comprises: - a first, central portion (14a) which extends from the output opening (11) to the first vertical conveyor means (15) , and in which the horizontal screw is oriented in a manner such as to transport the material from the lower output opening (11) to the vertical conveyor means (15) , and - a second, outer portion (14b) which extends on the outer side of the first vertical conveyor means (15) and in which the horizontal screw is oriented in a manner such as to transport the material from the exterior towards the vertical screw conveyor (15) , the portions being arranged as extensions of one another. 3. A drier according to Claim 2, characterized in that the outer portion (14b) of the horizontal screw conveyor (14) is arranged for receiving the moist material to be dried from a further loading conveyor means (17) coupled to the second portion (14b) in order to discharge therein the material to be dried. 4. A drier according to Claim 3, characterized in that the outer, loading conveyor (17) is rotated by transmission members (18) connected to the horizontal screw conveyor (14) . 5. A drier according to Claim 1, characterized in that one or more of the horizontal screw conveyor means (14) has a connection means (16) for receiving rotary drive from an external drive unit . 6. A drier according to Claim 2, characterized in that the first portion (14a) and the second portion (14b) of the horizontal screw conveyor means (14) are connected by an intermediate portion having a radial blade (24) which can direct the material transported into a chamber (23) which contains the foot of the vertical screw conveyor means (15) . 7. A drier according to Claim 1, characterized in that the blades (21) of said mixer device are spoon-shaped. 8. A drier according to Claim 7, characterized in that the material collected in said drying chamber (10) is forcedly directed towards the output opening (11) in a substantially radial direction.

Inventors: BARBIERI SILVANO, BARBIERI, SILVANO
Applicants: AGREX SPA, BARBIERI SILVANO, AGREX S.P.A., BARBIERI, SILVANO
Application year: 1999
Main classification: F26B9
IPC codes: F26B9