The present invention is for an apparatus for heating and drying, wherein the desired results are mainly obtained by the use of microwaves. Heating and drying wih microwaves brings with it considerable advantages but also special problems, especially when handling large objects and in large plants. In such plants a great number of microwave generators are used, the function of which shall be monitored and controlled in several respects, for example the supply of energy per unit time and the temperature of the goods. It is also important that the microwaves cannot reach out of the apparatus and that other losses of energy as far as possible are avoided.

The present invention is for an apparatus for heating and drying which takes the shape of a tunnel having several microwave generators positioned along the tunnel. There are also arrangements for continuous conveyance of goods through the tunnel which by being divided into section makes it possible to recondition the goods between sections having microwave heating.

The invention will below be described more in detail with reference to the examples of embodiments of the invention which are shown in the enclosed figures.

Figure 1 shows an apparatus according to the invention and a conveyor car thereof.

Figure 2 shows in principle the layout of the expended system according to the invention.

The apparatus shown in figure 1 has a tunnel 1 with opening sections 5 and 6. The goods which shall be treated is conveyed through the tunnel on a car 2 and in the example shown in the

figure this goods is timber which is conveyed through the apparatus for drying. The car 2 has in one of its ends a gable wall 7 which includes a board that is impermeable to the microwaves. The gable is surrounded by a frame 8 having microwave baring properties and an outer dimension which is close to the inner dimensions of the tunnel. The tunnel 1 in the whole has a constant cross section.

When the goods is conveyed through the tunnel carried by cars having microwave impermeable gables, the tunnel is thereby divided into sections. Microwave generators 3 A-C, 4 A-C are positioned along the tunnel at both sides thereof. The distance between consecutive microwave generators and the length of the cars can be selected in a desired relationship to each other, when the respective units are designed and manufactured. The microwave generators suitably are equipped with individual control devices and, therefore, the energy supplied to each section can be carefully controlled.

The gable walls also have a function to divide the tunnel into several separate spaces or zones, wherein the conditions can be individually controlled, for example by ventilation. This is obtained by means of fans 12 and one may hereby in known ways make use of the cooling air from the microwave generators. For some applications it is also possible to arrange separate cooling fans, by which air from the surroundings is blown into some sections of the tunnel.

The cars onto which the goods is conveyed through the tunnel are individually designed for different applications. Besides the application of timber drying already mentioned, this kind of devices may also be used for drying of painted or laquered objects and for other purposes. Instead of cars the goods can be conveyed through the tunnel by means of different kinds of conveyors, for example chain or wire conveyors which preferably are arranged in the floor or the ceiling of the tunnel. The gable walls are then designed so that they instead follow the

conveyor, being permanently or detachably mounted thereto.

The plant as shown in figure 2 has three adjacent tunnels 1, 10 and 11. At right angle to the tunnel 1 there is an inflow section 9, wherein the cars are positioned across the length of the section waiting to be conveyed into the tunnel. This plant shows as an example the flexibility and possibilities in the layout of a heating and drying apparatus according to the invention.

The apparatus and devices may within the scope of the invention be varied in various respects. For example, the individual cars or corresponding sections of a conveyor may carry microwave impermeable gables at both ends. They may also be made as containers in which the goods to be treated is placed. The goods may then be comparatively small units and it may also have irregular shape and size. The containers are made from a suitable material for this purpose, for example such as is only to a minor extent affected by the microwaves and thus is not heated by direct influence from them.