There are agricultural implements which use airflow to transport granular or powder material, such as seed, fertilizer or pesticide, from a feed device to one or more applicators, such as sowing shares or fertilizer shares.
Some agricultural implements of this kind use one or more fans of the centrifugal type in order to produce the airflow. A centrifugal fan normally comprises a fan housing, in which an impeller is rotatably disposed. By the radially central portion of the impeller, an inlet opening, through which air can be sucked in, is found in the fan housing. By the radially peripheral portion of the impeller, an outlet opening, through which air can be blown out, is found in the fan housing. The outlet opening is often directed substantially tangentially relative to the impeller.
The outlet opening can be connected to a tube or a pipe, which conducts air to, for example, a seed feeder.
The fan housing usually has a wall with curved inner surface, which, apart from the outlet opening, extends around the whole of the impeller so that the fan housing can be said to be “worm-shaped”.
When a centrifugal fan is to be used to feed air to a plurality of consuming devices, branch pipes or Y-couplings connected to the outlet opening can be used to distribute the air from the outlet opening.
FIG. 1 shows an agricultural implement in the form of a sowing machine 200, which is pulled by a towing vehicle in the form of a tractor 300. The sowing machine 200 has a fan 201 for producing a feed airflow, an air duct 202 for conducting the feed airflow to a seed feeder 204, the function of which is to meter and to, using the airflow, feed seed via pipes or tubes 205 to sowing shares 206. The seed feeder 204 can be arranged below, or form a lower part of, a container (also referred to as “seed box”) 203, so that the seed feeder 204 is filled with seed from the seed box 203 by the action of gravity.
In applications in which there is a limited supply of drive power, which can be the case with agricultural implements, it is desirable to improve the overall efficiency of the fan and its associated branch pipes or Y-couplings.
In applications to mobile units, such as agricultural implements, it is also desirable to minimize the spatial requirements by providing a fan and a branch arrangement which is as compact as possible.
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