GB2091983A

GB2091983A - A centrifugal spreader

Info

Publication number: GB2091983A
Application number: GB8137431A
Authority: GB
Original assignee: Amazonen Werke H Dreyer SE and Co KG
Current assignee: Amazonen Werke H Dreyer SE and Co KG
Priority date: 1980-12-24
Filing date: 1981-12-11
Publication date: 1982-08-11
Also published as: FR2496390A1; DE3049070C1; NL8105365A; FR2496390B1; GB2091983B

Abstract

A spreader has two centrifugal discs (2) which are interchangeable with other discs and arranged on a respective drive shaft (23). In order to change the spreading pattern of the spreader in such a manner that field edge strips can be covered with the same quantity of fertiliser per unit area; i.e. spreading density, as the rest of the field, without fertiliser being thrown beyond the edge of the field, a centrifugal border disc (9) also provided with throwing elements is provided. The border disc (9) is selectively mountable on one or the other of the two drive shafts (23). Furthermore the border disc (9) has at least one radially extending throwing element (14) as well as at least two throwing elements (15) which are arranged angularly symmetrically at an acute angle beta to respective tangents (17) to the circular path (16) of the outer edges of the throwing elements (15). The outer edges of the throwing elements (14, 15) of the border disc (9) have a smaller spacing from the drive shaft (23) than the outer edges of the throwing elements of the discs (2). <IMAGE>

Description

SPECIFICATION A centrifugal spreader The invention relates to a centrifugal spreader particularly but not exclusively for spreading fertiliser and more particularly concerns a centrifugal spreader having a spreading device comprising two centrifugal discs provided with throwing elements, each centrifugal disc being releasably mounted on a drive shaft so as to be interchangeable with other centrifugal discs.

Such a spreader is known from Fed. Rep. of Germany Auslegeschrift 28 05 879. In this known spreader the centrifugal discs can be interchanged with discs having different ejection angles. Hence, it is possible to change the effective spreading width by changing the discs.

However, this known spreader suffers the drawback that, it is only possible to attain, with available discs, spreading patterns having both sides edge zones which run out either in a flat of in a steep manner.

When the spreader is fitted with centrifugal discs by means of which a spreading pattern is obtained with edge zones that run out steeply, the spreader is admittedly better suited for spreading over edge strips of a field, than when fitted with the other thrower discs, since much smaller quantities of fertiliser are spread over adjacent fields, bordering paths or into ditches, while a uniform spreading density is maintained as far as the edge of the field.Nevertheless even these quantities are still too large for many conditions taking into account protection of the environment, so that it is unavoidable that the edge strips of a field should be treated with a spreading density which decreases outwardly. Moreover, it is a disadvantage of a spreading pattern of this kind that it is very sensitive to cross wind; i.e. that even a small lateral displacement of the spreading pattern, for example owing to a lateral wind, has such an unfavourable effect that strips provide with highly excessive or insufficient fertiliser are produced within the overlap zones of the individual spreading paths. Furthermore, a very accurate joining travel is a condition for uniform spreading over the entire field surface.

In contrast when the spreader is fitted with the centrifugal discs which produce an edge zone spreading pattern running out in a flat manner, it has the great advantage that joining travel is required which is not too accurate, because the edge zones overlap to a large extent and thus a sufficiently uniform spreading density over the entire surface to be covered is obtained even with slight lateral displacement of the spreading paths relative to each other. In contrast thereto edge strips of a field cannot be fertilised at all with sufficient spreading accuracy by means of such discs if large quantities of fertiliser must not be thrown beyond the edge of the field.

Furthermore, a spreader is known (see Fed.

Rep. of Germany Offenlegungsschrift 200 04 253) which has two centrifugal discs fitted with throwing elements, to which the fertiliser is fed independently of each other in adjustable quantities.

This last mentioned spreader is characterised in that during the spreading operation a spreading pattern is obtainable which is symmetrical not only in itself, but also in relation to the centre of the spreader. On the other hand it is possible, by cutting off the supply of fertiliser to one disc, to reduce to one half the effective spreading width of the machine, so that a spreading pattern is produced which is offset laterally from the centre of the spreader. Although by this measure it is possible to spread fertiliser over narrower edge strips of a field, the spreading pattern obtained with only one thrower disc is approximately symmetrical in itself, and the same disadvantages for covering a field edge occur as with the first mentioned spreader.

The invention seeks to provide a spreader able to change its spreading pattern in such a manner that even when the effective spreading width is maintained edge strips of a field may be covered with the same quantity of material e.g. fertiliser per unit area; i.e.

spreading density, as the rest of the field, without material being thrown beyond the edge of the field. In this case maintenance of the effective spreading width at the edges of the field is advantageous in particular when the spreader is employed in connection with the travel rnw method.

The invention provides a centrifugal spreader having a spreading device comprising two centrifugal discs provided with throwing elements, each centrifugal disc being releasably mounted on a drive shaft so as to be intershangeabBe with other centrifugal discs, wherein a centrifugal border disc also provided with throwing elements is provided, the border disc being selectively mountable on one or the other of the two drive shafts, and wherein the border disc has at least one radially extending throwing element as well as at least two throwing elements which are angularly symmetrically arranged at an angle (p) to respective tangents to the circular path circumscribed by outer edges of the throwing elements, and where the respective throwing elements touch said path and wherein the outer edges of the throwing elements of the border disc have a smaller spacing from the drive shaft than the outer edges of the throwing elements of the first-mentioned discs.

Hence a spreading pattern can be obtained which has a spreading density which decreases steeply in an outer edge zone. This is caused by the fact that fertiliser particles are thrown less far outwardly on the one hand by the adjustment or arrangement of the thrower elements, and-on the other hand by the reduction in the spacing of the outer edges of the throwing elements from the drive shaft; i.e. by reduction of the ejection velocity. Consequently, on the side of the spreading pattern facing the inner region of the field the advantageous large overlap of the edge zones can be maintained whilst a sufficiently large spreading density can be obtained at the field edge, without wastage of fertiliser.

Preferably, the direction of rotation of the border disc is reversable with mirror-symmetrical change of the spreading pattern in order that only one border disc need be provided in spreaders having a spreading device in which the outer drive shafts of the discs rotate in mutally opposite directions.

Preferably, the angles between the central regions of the throwing elements have the same magnitude in order to obtain a particularly advantageous distribution of fertiliser.

Preferably, at least two border discs with different vertical ejection angles are provided, in order to be able to utilise the advantages of the border discs for normal fertilisation as well as for late fertilisation.

Furthermore, advantageously, at least one holder for the centrifugal discs or for the centrifugal border discs, is provided on the spreader. Consequently, the required centrifugal or centrifugal border discs are always present at the location of employment of the spreader.

The invention will now be more particularly described, by way of example, with reference to the accompanying drawings, wherein: Figure 1 is a rear view of one embodiment of a centrifugal spreader according to the invention, and illustrating various spreading patterns, Figure 2 is a plan view of the border centrifugal disc of the spreader of Fig. 1, and Figure 3 is a section taken along line Ill-Ill of Fig. 2.

Referring to Fig. 1, the centrifugal spreader 1 shown therein is equipped with interchangeable centrifugal discs 2. A storage container 3 from which the fertiliser is supplied to the discs 2 in adjustable quantities in a known and therefore not illustrated manner, is arranged above the discs 2.

When using the centrifugal spreader 1 with the discs 2, a symmetrical spreading pattern 4, with edge zones 5 running out flat, is produced. This pattern 4 is defined on the left hand side of the centre line 6 by the full line 7 and on the right hand side of the centre line 6 by the broken line 8.

If however, the right hand disc 2 is interchanged with a centrifugal border disc 9 which, during non-use, is attached to the spreader 1 by means of the holder 10, an asymmetric spreading pattern 11 is produced which has edge zone 1 2 which decreases steeply on the right of the centre line 6.

Hence, a spreading density S is obtained while the effective spreading width E is maintained up to the field edge 1 3.

The border disc 9 is illustrated in Fig. 2 and is fitted with the throwing elements 14 and 1 5. The throwing elements 14 extend radially outwards, whereas the throwing elements 1 5 are arranged on the border disc 9 mirrorsymmetrically at an angle P (of less than 90 ) to respective tangents 1 7 to the circular path 1 6 circumscribed by the outer edges of throwing elements 1 5 where the throwing elements touch said path.Owing to such an arrangement of the throwing elements 1 5 it is possible to drive the border throwing disc 9 in the direction of rotation 1 8 and also in the direction of rotation 1 9. In this case in order that the spreading patterns resulting from the individual throwing elements 14, 1 5 may overlap uniformly, the angles y between the throwing elements are of equal magnitude.

The border throwing disc 9 is connected to one of two drive shafts 23 so as to rotate therewith by means of a hub 20, a groove 21 and a feather key 22. It is merely necessary to push the disc 9 onto the drive shaft 23 and to secure it against displacement by means of a fastening device 24.

Fig. 3 shows the border disc 9 with a vertical ejection angle (owe) at which the fertiliser particles are projected from the disc. For normal fertilisation a border disc 9 having a small ejection angle should be selected, and for late fertilisation a disc having a larger ejection angle should be selected.

The throwing elements 1 5 are angularly symmetrically arranged in such a manner that the throwing element 25 which in the direction of rotation 1 8 has its outer edge leading its inner edge, delivers the steeply decreasing edge zone 12, whereas the throwing element 26 which, in the direction of rotation 18 has its outer edge, lagging behind its inner edge, ensures a gradual decrease 27 of the spreading density. The radially extending throwing elements 14 fill in a region 28 between the regions 1 2 and 27 covered by the throwing elements 15, up to the uniform spreading density S.

Claims

1. A centrifugal spreader having a spreading device comprising two centrifugal discs provided with throwing elements, each centrifugal disc being releasably mounted on a drive shaft so as to be interchangeable with other centrifugal discs, wherein a centrifugal border disc also provided with throwing elements is provided, the border disc being selectively mountable on one or the other of the two drive shafts, and wherein the border disc has at least one radially extending throwing element as well as at least two throwing elements which are angularly symmetrically arranged at an angle P to respective tangents to the circular path circumscribed by the outer edges of the throwing elements, and where the respective throwing elements touch said path and wherein the outer edges of the throwing elements of the border disc have a smaller spacing from the drive shaft than the outer edges of the throwing elements of the first-mentioned discs.

2. A centrifugal spreader as claimed in claim 1, wherein means are provided for feeding fertiliser to the centrifugal discs, mounted on the drive shafts, independently of each other in adjustable quantities.

3. A centrifugal spreader as claimed in claim 1 or claim 2, wherein the direction of rotation of the centrifugal border disc is reversable with a mirror-symmetrical change of the spreading pattern.

4. A centrifugal spreader as claimed in anyone of the preceding claims wherein the angle y between the central regions of the throwing elements are of equal magnitude.

5. A centrifugal spreader as claimed in anyone of the preceding claims, wherein at least two centrifugal border discs are provided which have different vertical ejection angles CL.

6. A centrifugal spreader as claimed in anyone of the preceding claims, wherein the spreader is provided with at least one holder for holding the centrifugal discs when not in use.

7. A centrifugal spreader substantially as hereinbefore described with reference to and as shown in the accompanying drawings.