The present invention relates to an assembly for a drying plant for materials, especially bales of grass fodder, comprising a drying chamber having flexible walls which is intended to be supplied with drying air through one or more inlets, and wherein the used air is passed out through outlet openings.

In addition to grass fodder, such as hay and straw, the invention can also be used for drying wood, lumber, various waste products from agruculture, from forestry opera¬ tions, etc.

Conventionally, when artificially drying such materials, the materials in question are stacked in a drying chamber and drying air is blown into the chamber and passes more or less through the materials. Such a drying system requires, firstly, a stationary plant, or at least a plant which is not easily mobile _? secondly, one obtains poor utili¬ zation of the drying air, since a large proportion of the air will flow through the chamber without having passed through the materials which are to be dried.

In agriculture, for example, there is a very great need for effective drying devices for various purposes, especially in our climate. In rainy summers, it is very difficult and expensive to get the hay dried in the fields. Artificial drying has not hitherto been widely used, and with the systems known to date it is very expensive. Straw, too, normally has a relatively high moisture content, and it will be ruined if it is stored in a packed, baled state without having been dried first.

The object of the invention is thus to provide a drying assembly of the type defined introductorily, which is characterized in that the drying chamber consists of a flexible sack whose bottom is guided inside the sack so as to form a double-walled bell, that an inlet for admitting drying air into the space between the walls is provided in

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the outer wall, that a plurality of inlets for admitting draft air to the drying chamber are provided in the inner wall, that the open side of the drying chamber (bell) is closed by a wall having a plurality of outlet openings for the used drying air, and that the collective cross-sectional area of the draft openings in the inner wall is dimensioned such in relation to the amount of air supplied that an overpressure is produced in the intermediate space between the walls.

In accordance with the invention, the draft opening in the inner wall are preferably provided in the bottom of the sack, i.e. , that portion of the drying chamber which lies opposite the mouth or opening of the bell. In a practical embodiment of the invention, the inlet for admitting drying air is formed by the neck opening of the sack, which is drawn together so as to have a smaller cross section.

A characteristic feature of a practical embodiment of the invention is that the wall which closes the open side of the chamber (belli consists of a freight pallet having through openings therein to permit the exit of used drying air, e.g., a pallet of the "Europapall" type.

Because of the bell-shaped configuration of the drying chamber, and owing to the fact that there is an over¬ pressure in the intermediate space between the flexible walls of the chamber, the chamber seals tightly around the outer contours of the material which is to be dried. The air is blown in at one end of the chamber and is forced through the materials which are to be dried, exiting at the opposite end of the chamber. Thus, all of the drying air is effectively utilized for drying, since in effect almost no drying air is permitted to pass outside the material to be dried. The drying chamber according to the invention is also very inex¬ pensive to produce. One can use, e.g., reinforced plastic for the flexible bell-shaped chamber, and if a freight pallet of the type mentioned above is used to close the open side of the bell-shaped chamber, one will obtain a very inexpensive drying plant. When collapsed, the drying apparatus takes up very little space and is. easy to transport. Thus, a farmer, for example, could use this system to dry hay and straw out

in his fields. Partially-dried hay or straw is pressed into bales by means of a baler and the bales are placed on the pallets. Thereafter, the sack is pulled down over the bale or bales, the bottom of the sack being placed on the top of the bale and the sack then being drawn down over the side walls of the bale. The lower margin of the bell-shaped chamber is fastened to the pallet, and the neck end of the sack is connected, for example, to branch connections on a pipe which supplies hot drying air.

The invention will be explained in greater detail in the following with reference to the accompanying drawings, wherein

Figure 1 shows a drying assembly according to the invention in cross section, and

Figure 2 illustrates the manner in which several of the assemblies of Figure 1 may be connected to a common source of drying air.

The drying assembly consists of a flexible sack 1 whose bottom 2 is guided inside the sack so as to form an open bell. In practice, this is done in that the bottom 2 of the sack is placed on top of the material to be dried, e.g., a bale of grass fodder 3, and the sack is then pulled down over the bale. In this way, one obtains a downwardly-open, bell-shaped drying chamber 4 having double walls, i.e., an outer wall 5 and an inner wall 6. The open side of the drying chamber is closed by means of a wall, e.g. , a freight pallet 7 having an open grid structure, of the "Europapall" type. The flexible bell is fastened to the pallet by means of fastening means, e.g., elastic hooks 8. The bottom 2 of the sack is provided with a number of draft openings or holes 9. The open, neck end of the sack is drawn together into an inlet opening 10 which is connected to a source of hot air, for instance, the pipe 11 in Figure 2. The collective area of the opening ^' s 9 is dimensioned such in relation to the amount of air which is introduced through the opening 10 that an overpressure is produced in the space 12 between the outer wall 5 and the inner wall 6. The sack will thus be filled with air with a certain overpressure in the intermediate space 12, such that the outer wall 5 bulges outwardly while

the inner wall 6 will be pressed tightly against the bale 3. The air will be pressed in through the draft openings 9 as shown by the arrows and forced through the material being drie e.g., the bale 3, leaving the drying apparatus through opening in the underlying pallet 7. It is obvious that instead of a pallet 7, one could utilize another type of wall or floor having openings therein for closing the open side 13 of the drying chamber. Neither is it required that the open side of the drying chamber face downwardly, but this is the most practical configuration. In this way, the material to be dried, e.g., a bale 3, can be placed on a pallet which rests on a reasonably horizontal foundation.

In Figure 2, six drying chambers 1 have been assembled, their respective neck ends 10 being connected to a common pipe 11 for supplying drying air. If such a system is placed out in a field, one can avoid the costly transportation of the heavy, moist bales. In the case of hay, the bales can then be transported to their storage site, for example, a hayloft, in a dried state. In the case of straw, the dried bales can be stored beneath plastic in the field and treated in situ with ammonia gas.