The present invention relates to an accessory for a potato harvester. ' A potato harvester generally comprises a digging device which digs up and separates the potatoes from the soil, and conveyors which bring the potatoes into a collecting container. The harvester is driven e.g. by a tractor on a field. After being harvested, the potatoes are taken to a storage.

Potatoes are not sorted before storage. Unsorted potatoes are preserved in storage much better than sorted potatoes. If the potatoes are sorted in storages containing potatoes from different growers, this may involve the risk of spreading diseases or pests. The sorting of the potatoes is mainly carried out in the storages according to the demand of consumers and food industry, and sorted potatoes are not held in storage. However, this often has the result that there are sufficient stocks of unsorted potatoes but they cannot be brought to the market because there is no demand for certain sorts of potatoes. It should also be noted that, in Finland, the sorting of seed potatoes is only allowed in the spring, in the month of April.

The object of the present invention is to pro¬ vide a new accessory for a potato harvester that enables potatoes to be sorted into suitable fractions according to size immediately in connection with harvesting. This is achieved by virtue of the features characteristic of the invention as presented in claim 1.

The device of the invention allows immediate sorting of potatoes in connection with mechanical har¬ vesting. The potatoes can thus be sorted into desired fractions according to size during harvesting, and dif¬ ferent fractions can be stored separately. This means that it is no longer necessary to use expensive sorting equipment and operating personnel at the storages. Sorted potatoes can be stored in large containers, from

which they are packed into bags or similar transport packages for distribution to consumers and/or food in¬ dustry according to demand. It is also to be noted that the potato quality is significantly improved because the potatoes need not be subjected to so many handling operations. Besides, the differences in the demand for potatoes of different sizes will not affect the availa¬ bility of potatoes from storages. Thus, the annual potato crop will be utilized in the best possible way while an optimal potato quality is maintained.

The device of the invention also has the im¬ portant advantage that using the device will not render the harvesting itself either slower or more difficult. The sorting takes place automatically during harvesting and the sorted potatoes are collected in different containers according to size.

Moreover, the device of the invention is simple in construction and easy to maintain and has a basic construction that allows it to be easily fitted to different types of potato digger.

In the following, the invention and its other advantages are described in detail by referring to the appended drawings, in which

Fig. 1 presents a top view of the device of the invention as connected to a potato harvester; Fig. 2 shows the device in Fig. 1 as sectioned along line A-A;

Fig. 3 presents the device in Fig. 1 as seen from direction B;

Fig. 4 shows a partial section through another embodiment of the potato harvester accessory of the invention;

Fig. 5 the device of Fig. 4 as seen from direction C; Figs. 6, 7 and 8 present screens and screen guides as used in the device in Fig. 4.

A potato harvester comprises a digging ap¬ paratus which digs up and separates the potatoes from

the soil and brings them onto a conveyor or conveyors, which then convey them to a collecting container. The drawings do not show the complete potato harvester because the invention only concerns an accessory for a potato harvester. The illustrations present a conveyor 1 and a container 2 for collecting the potatoes. The conveyor 1 brings the potatoes into the container 2.

The potato harvester accessory of the invention is provided with a screening set 3 comprising at least one screen 31 and at least one auxiliary collecting container 4. By means of the screens, the potatoes are sorted into two or more fractions according to size and passed further into the collecting container 2 and one or more auxiliary containers 4.

The embodiment illustrated by Figs. 1, 2 and 3 comprises a screening set 3 provided with one screen 31 and one auxiliary collecting container 4. The screening set 3 is mounted on the upper part of the collecting container 2 of the potato harvester. The size of the apertures 31a of the screen 31 is such that a fraction of the potatoes brought onto the screen by the conveyor will pass through. The auxiliary container 4 is fitted beside the collecting container 2 of the potato har¬ vester. Potatoes not passed through the screen 31 are directed into this auxiliary container 4.

The accessory described above has been designed for the sorting of potatoes into two fractions according to size in connection with harvesting. Such sorting is especially important for estates specializing in the production of seed potatoes. The preferable size of seed potatoes is in the range 28-50 mm (average diameter) . The lower limit for all varieties is 28 mm, but the upper limit varies between 45 - 55 mm., depending on the variety.

The preferable mesh size 31a of the screen 31 is 45-55 mm. In this case, seed potatoes and small-sized

potatoes in general will be gathered in the collecting container 2 of the potato harvester while bigger-sized potatoes are collected in the auxiliary container 4.

So far, a problem in mechanical harvesting of seed potatoes has been the proportion of large-sized potatoes. In a normal crop, about 80% of the potatoes are of seed size and 20% of a size exceeding seed size. When seed potatoes are marketed, this proportion of 20% is generally lost.

The accessory of the invention makes it pos¬ sible to separate the larger-than-seed-size fraction from a seed potato crop during harvesting. The oversized potatoes can then be sold as food potatoes to consumers or food industry.

In the embodiment illustrated by Figs. 4 - 8, the accesory of the invention has a screening set 3 comprising two screens 31, 32 and two auxiliary col¬ lecting containers 41, 42. One of the screens 31, 32 is placed at a distance on top of the other. The screening set 3 also has a bottom part 33 located below the screens 31,32. The screens 31,32 and the bottom part 33 are provided with guides 31b, 32b, 33b respectively. The apertures 31a of the upper screen 31 are larger than those 32a of the screen 32 below it.

Figs. 6, 7 and 8 illustrate individual struc¬ tural parts of the screening set 3. The guides 31b, 32b and 33b are so arranged in connection with the screens 31,32 and the bottom part 33 that the potatoes brought onto the screening set 3 by the conveyor 1 can be sorted into three fractions according to size and collected in the auxiliary containers 41,42 and the main collecting container 2.

The screening set 3, the screens 31,32 and corresponding parts, e.g. the bottom part 33, are pre¬ ferably provided with a coating made of a resilient ma¬ terial, such as rubber. The coating effectively protects the potatoes against damage during screening.

The screens 31,32 are preferably lattice screens with square apertures 31a, 32a. Such screens are easy to manufacture and they are well suited for the sorting of potatoes.

The screening set 3 is replaceably fitted onto the top part of the collecting container 2 of the potato harvester. This provides an advantage when the variety of potatoes to be harvested is changed. The screens 3 can thus be optimally selected with respect to mesh size 31a, 32a and the potatoes can be sorted in the desired way.

In the embodiments illustrated by the drawings, Figs. 2 and 4, the screening set 3 is placed in an oblique angle α so that it slopes towards the auxiliary collecting container 4; 41, 42. In addition, the screening set 3 is preferably provided with a moving mechanism 5, by means of which the screening set 3 is moved back and forth mainly in the direction of incli¬ nation of the screens.

In this case, one end 3b of the screening set 3 is mounted on the collecting container 2 or structural parts connected thereto, e.g. on the transverse bar 6 provided in the upper part of the container. The other end 3c of the screening set 3 is supported by appropriate structural parts from below and is outside container 2 and above container 4.

In the embodiments illustrated by the drawings, one end 3b of the screening set 3 is suspended on the transverse bar 6 by means of swivelling arms 7. The other end 3c of the screening set 3 is supported from below by swivelling arms 8 mounted on the collecting container 2 of the potato harvester, in this case espe¬ cially on the structures 9 supporting the second con¬ tainer 4. The swivelling arms 7,8 prevent lateral motion of the screen. In this way the screen 3 is firmly mounted in conjunction with the container 2, yet so that it is easily movable in the longitudinal direction.

The appropriate wall of the container 2 of the potato harvester is provided with an opening 10 through which one end 3c of the screening set 3 can pass. The width of the opening approximately corresponds to the width of the screening set and has a height that enables the screens to move in it and the potatoes to roll out over the screens into an auxiliary container 4; 41, 42.

In the embodiment illustrated by Figs. 4 and 5, the screens 31, 32 and the bottom part 33 are provided with guides 31b, 32b, and 33b, respectively. Guide 31b directs the potatoes not passed through the screen 31 into the main collecting container 2. Guide 3lb consists of two curved or straight parts placed in a perpendicular position relative to the surface of the screen 31. The ends of these two parts are joined together at the middle line of the screen and the parts spread out towards the edges in a plough-like fashion as shown in Fig. 6.

The second screen 32 is likewise provided with a guide 32b. This is a straight or a curved part placed in a position perpendicular to the surface of the screen 32 and it extends from one edge of the screen obliquely to one end 3c of the screening set so that it will guide the potatoes not passed through the screen 32 to one side and to the end 3c of the screen (see Fig. 7) , from where they will fall down.

The bottom part 33 of the screening set 3 con¬ sists of a solid plate provided with a guide 33b, which is similar to the guide 32b of screen 32. However, guide 33b is placed at the opposite .edge of the bottom part as compared to the guide 32b of the second screen 32. In this way, guide 33b directs the potatoes passed through screen 32 to the opposite edge of the screen end 3c (see Fig. 8) .

In this embodiment, the first screen 31 in the screening set 3 has a mesh size of approx. 50 mm while

the preferable mesh size of the second screen 32 is in the range 30 - 40 mm.

In this case, the container 4 provided for the screening set 3 is divided e.g. into two compartments, one of which receives the potatoes which have not passed through screen 32 while the other receives those which have passed through it and move forward along the bottom 33.

The device of the invention can also be fitted on the container 2 of the potato harvester without an opening 10. In this case, the end of the conveyor 1 must be placed higher up and/or the container must be placed lower down to allow the screening set 3 and associated equipment to be fitted between the conveyor 1 and the container 2.

The moving mechanism 5 comprises a power means, e.g. a hydraulic motor 5a, with a wobbler 5b connected to its power transmission shaft. A power transmission element 11, e.g. a rod, is provided between the screening set 3 and the wobbler 5b. In this case, the rod 11 serving as a power transmission element is turnably attached by its ends to the screening set 3 and the wobbler 5b. The hydraulic motor is mounted on the container 2 using suitable supports 15.

The auxiliary collecting container 4 in Figs. 1, 2 and 3 is fitted beside the main container 2 of the potato harvester with the aid of supporting structures 9. In this case, the supporting structures consist of a pair of vertical bars 9a, which are attached at least to the supporting structures of the container and to the frame of the potato harvester. Furthermore, the supporting structures comprise at least two horizontal bars 9b, which are attached to the above-mentioned vertical bars 9a in a suitable manner, e.g. by welding. The auxiliary container 4 rests on the horizontal sup¬ ports 9b. In addition, the container 4 is attached to the outer edge of the supporting structures, i.e. to

the ends of the horizontal supports 9b, using trunnions 12 or equivalent. Fitted between the supporting structure 9 and the container is at least one compression cylinder 13, by means of which the container 4 can be turned at least partially about the trunnions 12 to empty it. The sides of the container 4 are preferably provided with braces 14, to which the end of the compression cylinder 13 is attached.

In the embodiment illustrated by Figs. 4 and 5, the auxiliary container 4 is divided into two separate containers 41 and 42. These containers are preferably mounted beside the main container 2 of the potato harvester with the aid of supporting structures 9 in the way described above. The collecting containers 41 and 42 are supported by trunnions 12 on the ends of the horizontal bars 9b. Each container 41, 42 is provided with its own compression cylinder 13a, 13b and mounted on the potato harvester in the same manner as the above-described auxiliary container in Figs. 2 and 3. By means of the cylinders 13a, 13b, the auxiliary containers 41, 42 can be emptied separately, independently of each other.

In principle, a potato harvester provided with the sorting device of the invention works as follows. The harvester digs up the potatoes in the normal manner, and the conveyor brings them into the containers. From the conveyor, the potatoes fall down onto the screen 3, which is moved to and fro by the moving mechanism 5. Potatoes of a maximum size corresponding to the size of the apertures 31a, 32a of the screens 31, 32 are passed through the screens. Potatoes exceeding the mesh size will roll over the screens and smaller potatoes will roll along the bottom 33 (if the screening set 3 is provided with a bottom part 33) towards the opening 10 and/or the guides 31b, 32b, 33b and further into an auxiliary container 4; 41, 42 and the main collecting container 2. In this way, the potatoes are sorted

directly during harvesting. In the case of the embodiment illustrated by Figs. 4 and 5, large-sized potatoes are collected in the main container 2 while smaller potatoes are collected in the auxiliary con¬ tainers 41, 42. The containers 4; 41, 42 are easily emptied at suitable intervals by means of the compres¬ sion cylinder 13; 13a, 13b e.g. onto the trailer of a tractor.

The auxiliary container 4; 41, 42, mounted in conjunction with the main container 2, is placed at a suitable height relative to the trailer height to allow convenient emptying. If necessary, the mounting height of the auxiliary container 4; 41, 42 can be adjusted to a suitable level with respect to the main container 2 by adjusting the position of the supporting structures 9.

In the foregoing, the invention has been described by referring to two preferred embodiments, but it is obvious that it can be implemented in many ways within the scope of the idea of the invention as defined in the following claims.