Method of spreading flowable material

Abstract: Method of spreading flowable material over a surface by means of a spreader device comprising at least two spreader discs (4,5) rotatable in two directions. The first direction of rotation is selected to be towards each other on the non-shielded side of the spreading apparatus (wide spreading). The other opposite direction of rotation is away from each other (narrow spreading). The first direction is used for spreading in the middle of the field. The other direction is used for spreading along the boundary (3). The spreader vanes on the spreader discs have different spreading characteristics when used in the two directions. The effective spreading distance is smaller for the spreader vane at the spreader disc (5) adjacent to the boundary (3), when driven away from the other disc (4) (narrow spreading). Without changing spreader discs or spreader vanes it is in this way possible to obtain an even and constant distribution of the material to be spread over the field from boundary to boundary.

Description: TECHNICAL FIELD The present invention relates to a method of spreading flowable material over a surface such as set forth in the preamble of claim 1. BACKGROUND ART A method of this kind is disclosed in EP 0835602. In this disclosure is described how the spreading pattern can be changed, e.g. with a view to be able to pass along a field boundary or a watercourse without spreading e.g. fertilizer beyond certain limits, by using a spreading apparatus with two discs and making these discs rotate in the same or opposite sense in different directions, and possibly blocking the supply of spreadable material to one of the discs. Said method has the drawback that the running track has to be substantially adjacent to the field boundary. In practice, however, the field is often divided in strips by fixed running tracks in such a way that the boundary spreading has to be done from the last running track, which is at a certain distance from the boundary. The distance between the boundary and the last - or first - running track is in practice determined by the working width of the machinery used on a specific farm and which in turn is selected from a few standard working widths. Thus, once a certain distance between the running tracks is chosen, all equipment must use that distance or a multiple thereof, including the spreading apparatus. Consequently, the location of the running tracks is predetermined, and the location of the running track for edge spreading is fixed. In the case that the last running track is not adjacent to the boundary, the method referred to above does not provide a possibility to spread evenly said flowable material over the strip between said running track and said boundary, without the need for changing the spreader vanes or other part of the spreader device. Changing the spreader vanes is a time-consuming operation and is thus undesirable. According to EP 0 880 877 A1 (document falling under Art. 54(3) EPC) or to EP-0 835 602 A1 a method for spreading material over a surface by means of a spreading apparatus is known, said device comprising at least two spreader discs each provided with one or more spreader vanes, where the spreader discs during operation can rotate either in opposite directions towards one another or away from one another on the non-shielded side of the spreader apparatus. During normal spreading operation, i.e. when spreading is performed at distances from the boundary of the surface large enough so that the casting distance of the spreader has not to be limited, the discs are rotated in opposite directions towards one another, whereas during spreading operations adjacent a boundary, where spreading is not allowed to take place across the boundary, the discs are rotated in opposite directions away from one another. The changed relative rotational directions of the discs results in changed spreading patterns due to specific construction of the spreader vanes. Another problem that arises with spreading from a distance from the boundary is the distribution profile of the material over the strip between the last running track and the boundary. The normal scatter profile is substantially inversely proportional to the distance from the spreading apparatus. This profile is supplemented by a pattern from the next track resulting in a uniform distribution of the material to be spread. There is however no next track for the edge spreading when spreading from a distance from the boundary. Therefore, the spreading pattern for the edge spreading must be such that it gives a substantially uniform distribution of material to be spread over the edge strip in one run. DISCLOSURE OF THE INVENTION On this background, it is the object of the present invention to provide a method of the kind referred to initially, with which it is possible to spread along the boundary of a field from a running track that is at a certain distance from the field boundary. This object is achieved in accordance with claim 1 by simply changing the rotation of at least one pair of spreader discs from rotating towards one another, i.e. wide spreading, to rotating away from one another, i.e. narrow spreading, when spreading along a boundary of the field. Moreover, the spreader vane or vanes of one of the spreader discs is/are designed in such a way that a reduced casting distance for the direction where the discs rotate away from one another is obtained and/or the rotational speed of the one of the discs is reduced in order to reduce the casting distance. Flowable material is supplied to both of the spreader discs, whereby the spreader disc that gives a reduced casting distance is used for spreading the strip between the boundary and the running track placed at a distance from the boundary. In this way it is possible to use the spreading apparatus for wide spreading when spreading in the middle of the field and for spreading to a boundary and still obtain an even and constant distribution of the flowable material over the total extent of the field from boundary to boundary. If the supply of flowable material to the spreader disc provided with spreader vanes giving a reduced casting distance is blocked, it is possible to use the spreading apparatus for spreading to the boundary even when the running track is adjacent to the boundary. This is due to the fact that the other spreader disc in the pair of spreader discs is driving in the narrow spreading mode because of the reversed direction of rotation, thereby distributing the material only to one side of the running track and by appropriate forming of the rear surface of the spreader vane obtaining the desired distribution. Together with the previously spread material from the wide spreading mode it forms a substantially uniform density over the area. BRIEF DESCRIPTION OF THE DRAWINGS In the following detailed part of the present description, the invention will be explained in more detail with reference to the exemplary embodiments shown in the drawings, in which Fig. 1 diagrammatically shows the running track plan for edge spreading from the field boundary together with the resulting distribution profile, Fig. 2 shows the running track plan for edge spreading from a running track at a certain distance from the field boundary together with the resulting distribution profile, and Fig. 3 shows an embodiment of a spreader vane giving a reduced casting distance when used for narrow spreading. DESCRIPTION OF THE PREFERRED EMBODIMENT Fig. 1 shows the running track plan for edge spreading from a track 1 adjacent the field boundary 3. The spreading apparatus is provided with a shielding means (not shown) to prevent spreading of said flowable material to e.g. the tractor on which the spreading apparatus is mounted. This limitation in the direction in which the flowable material can leave the spreader disc causes the scatter pattern of each spreader disc to be in the shape of a sector. During the normal spreading, i.e. not along a field boundary 3, the spreader discs 4,5 of the spreader device rotate towards one another on the non-shielded side of the spreading apparatus giving a casting distance B. This mode of operation is known as wide spreading. Since the spreader discs 4,5 rotate towards one another on the non-shielded side of the spreading apparatus, the spreading sectors of each disc 4,5 overlap one another to a great extent with a tendency to concentration in the area near the running track. After one drive along the track a mainly triangular distribution profile with the peak 7 in the track is obtained, as can be seen from the graph at the top of Figure 1. After the drive along the neighbouring track, the two triangular profiles are added resulting in a mainly constant and even density over the spreading width, cf. the hatching in section A-A. The casting distance B corresponds substantially to the predetermined distance between the running tracks. When spreading from the running track 1 along the field boundary 3, the direction of rotation of the spreader discs 4,5 is reversed so that the spreader discs 4,5 rotate in a direction away from each other on the non-shielded side of the spreading apparatus. The spreading sector of each disc 4,5 is thus reduced in such a way that their sectors are only slightly overlapping at the running track. This mode of operation is known as narrow spreading. If the supply of flowable material to the spreader disc 5 on the side of the field boundary is closed, the area along the field boundary can be spread, without casting material over the boundary. By an appropriate design of the rear surface of the spreader vanes of the discs to which the material is delivered the desired scatter profile of material can be obtained. The desired scatter profile is more precisely defined as being the quantities which together with one half of the previously distributed material from the passage of the neighbouring track with the spreader in the wide spreading mode result in a constant and even distribution to the boundary as shown in section A-A. Fig. 2 shows the running track plan for edge spreading from running track 2 at a certain distance of the field boundary 3. For non-boundary spreading the discs 4,5 rotate again towards one another on the non-shielded side of the spreading apparatus, and the spreading sectors of the discs 4,5 overlap. The spreader is operating in the wide spreading mode. For edge spreading from the track 2 at a distance from the field boundary 3, the direction of the spreader discs is reversed so that they spread away from one another on the non-shielded side of the spreading apparatus. This gives a small overlap over the running track 2 of the spreading sectors of the individual spreader discs 4,5. Due to the design of the rear surface of the vanes the spreader disc 4 situated furthest away from the field boundary will produce a normal casting distance so as to match the normal driving track plan as described above. The spreader disc 5 situated nearest to the field boundary 3 delivers a reduced casting distance b substantially corresponding to the distance between the driving track and the field boundary. This reduction in casting distance is achieved by using at least one spreader vane 10 that gives a shorter casting distance b and/or by reducing the rotational speed of the spreader disc 5. In the normal spreading direction of rotation this spreader vane will deliver the normal casting distance B. This effect is obtained by making use of both surfaces of the spreader vanes and by giving the vanes an appropriate design as explained in further details in the following part. An example of a spreader vane 10 that will give a reduced casting distance for one direction of rotation is shown in Fig. 3. This spreader vane 10 comprises a blade 12 having a first side 13 that comes in contact with the material to be cast for the normal direction of rotation and a second side 14 that comes in contact with the material to be cast for a second opposite direction of rotation, corresponding to the direction of rotation during edge spreading. The blade defines an aperture 15 that divides the blade in a radially inner section 16 and a radially outer section 17. The radially inner section 16 provides on said first side a surface 13 serving as a spring-board for the material to be spread so that the material to be spread can travel over the aperture 15 onto the radially outer section 17 from which it will be cast. The radially inner section 16 provides on said second side 14 of the blade a surface allowing the material to be cast to pass through the aperture 15. Since the material to be spread passes through said aperture 15 for the second opposite direction of rotation used with edge spreading, it will receive less kinetic energy than the material will receive when it is cast from said radially outer section 17 of the blade. In this way a reduced casting distance b is achieved for the opposite side of direction with a substantially equal speed of rotation of the disc. The reduction in casting distance can also be achieved by reducing the speed of rotation of the spreader disc. In this way a conventional spreader vane can be used. It is also possible to use said above-mentioned reduced casting distance spreader vane 10 in combination with a reduced rotational speed of the spreader disc in order to achieve said reduced casting distance b. According to the preferred embodiment of the invention the reduced casting distance b for the direction of rotation corresponding to the edge spreading will be substantially equal to half the normal casting distance B. Thus, the amount of material spread in the strip between the running track 2 not adjacent to the field boundary and the field boundary 3 will be substantially equal to the total amount of material spread with normal non-edge spreading. During normal field spreading each section of the field is spread on twice. Therefore, the strip next to the field boundary, on which is only spread once, will be spread with the right amount of material, if the normal amount of material is spread with half the normal casting distance. This demand is met by the above-described specific design of the rear surface of the spreader vane. The method of edge spreading from a running track 2 not adjacent to the field boundary can be carried out with any type of spreader vane that will give a reduced casting distance for one direction of rotation. Various modifications to the spreader vanes as presented in this application will be easily conceived by the skilled person. With the present invention it is possible to change between edge spreading from a track running in the field boundary and edge spreading from a track not adjacent to the field boundary without the operator of the spreader device having to make any modifications to the spreader device. If the spreader device is mounted to a tractor, it will be possible for the operator to select the desired method of edge spreading from the tractor without having to stop the tractor or leave the tractor and to make modifications to the spreader device. The operator has only to activate a simple device, which in turn will change the direction of the spreader discs and/or reduce the rotational speed of the spreader disc, and/or stop the flow of material to the outer disc. According to the invention, the reversal of direction of rotation of the spreader discs (4, 5) could also be achieved by providing two pairs of spreader discs, one pair rotating towards one another and the other pair rotating away from one another on the non-shielded side of the spreader apparatus and the flowable material being supplied selectively to either pair of spreader discs LIST OF REFERENCE NUMBERS 1 Track adjacent to boundary 2 Track at a certain distance from the boundary 3 Field boundary 4 Spreader disc 5 Spreader disc 6 Thick line 7 Peak B Casting distance b Reduced casting distance 10 Spreader vane with reduced casting distance 12 Blade 13 First side of blade 14 Second side of blade 15 Aperture 16 Radially inner section 17 Radially outer section

Claims: Method for spreading flowable material, preferably for spreading fertiliser, seeds or the like in granulate or powder form over an earth surface, by means of a spreading apparatus, comprising at least two spreader discs (4, 5), each provided with at least one spreader vane (10), the spreader discs (4, 5) being rotatable in two directions, comprising the steps of: (i) moving said apparatus along a running track (1, 2), (ii) when the distance between the boundary (3) and said running track is at least equal to the distance between adjacent running tracks, the direction of rotation of the spreader discs (4, 5) is such that they rotate in opposite directions (c, d) towards one another on the non-shielded side of the spreader device, (iii) when the running track is adjacent the boundary (3) rotating the spreader discs (4, 5) in opposite direction away from one another on the non-shielded side of the spreader device and closing the supply of flowable material to the spreader disc (5) closest to the boundary (3), characterised in that the method furthermore comprises the following steps the running track being at a distance from the boundary (3) said distance being less than the distance between adjacent running tracks: (iv) rotating the spreader discs (4, 5) in opposite direction away from one another on the non-shielded side of the spreader device and reducing the casting distance (b) of the disc (5) closest to the boundary (3) substantially to said distance from the boundary (3), said reduction of the casting distance being obtained by using at least one spreader vane (10) that gives a shorter casting distance and reducing the rotational speed of the spreader disc (5) closest to the boundary (3) or by using only at least one spreader vane (10) that gives a shorter casting distance , and (v) supplying flowable material to be spread to both of the spreader discs (4, 5) of said pair, whereby the spreader disc (5) with reduced casting distance is used for spreading material over the region between the boundary (3) and the running track. Method according to claim 1, characterised in that the change of direction of rotation of the spreader discs (4, 5) from towards one another to away from one another is achieved by using a transmission that can reverse the direction of rotation. Method according to claim 1 or 2, characterised in that said reversal of direction of rotation of the spreader discs (4,5) is achieved by providing two pairs of spreader discs (4, 5), one pair rotating towards one another and the other pair rotating away from one another on the non-shielded side of the spreading apparatus, the flowable material being supplied selectively to either pair of spreader discs. Method according to any of the preceding claims, characterised in that said spreader vane (10) comprises a blade (12) having a first side (13) that comes in contact with the material to be cast for a first direction of rotation and a second side (14) that comes in contact with the material to be cast for a second direction of rotation, whereby the first side (13) of the blade provides an engagement surface for the material to be spread that extends further from the centre of rotation than the surface of engagement provided by the second side (14) of the blade (12). Method according to claim 4, characterised in that said blade defines an aperture (15) dividing the blade in a radially inner section (16) and a radially outer section (17). Method according to any of the preceding claims, characterised in that the casting distance (b) obtained with spreader vane (10), that gives a reduced casting distance (b) for the direction where the spreader discs (4, 5) rotate away from one another, is approximately half the casting distance (B) obtained when the discs (4, 5) are rotated towards one another. Method according to any of the preceding claims, characterised in that said casting distance (B) obtained when the discs (4, 5) are rotated towards one another substantially corresponds to the distance between the running tracks. Method according to any of the preceding claims, characterised in that the reduced casting distance (b) substantially corresponds to the distance between the running track (2) and the boundary (3) of the area to be spread.

Inventors: LAURSEN NILS JORN, LAURSEN, NILS JORN
Applicants: LAURSEN AS A P, A.P. LAURSEN A/S
Application year: 1998
Main classification: A01C17
IPC codes: A01C17