Centrifugal spreader for granular materials with reduced metering

Abstract

Centrifugal spreader (1) for granular materials comprises at least one metering member (2) which has a dispensing opening (4) which can be throttled, adjustment means (9) for adjusting the throttling of the dispensing opening (4) so as to vary the flow rate of material to be spread which is supplied by falling to at least one corresponding centrifugal distributor (12) and a guide (15) which is interposed between the dispensing opening (4) of the metering member (2) and the centrifugal distributor (12) for conveying the material which is dispensed by the metering member (2) on the centrifugal distributor (12). The guide (15) includes a main channel (22) which extends between the adjustment means (9) and a material falling zone on the centrifugal distributor (12). The spreader (1) comprises an additional throttling member (40) which is associated with the guide (15) in order to further throttle upstream or downstream of the dispensing opening (4) the material flow which is dispensed from the dispensing opening (4) towards the guide (15).

Description

[0001] Centrifugal spreader for granular materials with reduced metering

[0002] DESCRIPTION

[0003] Technical field

[0004] The present invention relates to a centrifugal spreader for granular materials and the like, including the features mentioned in the preamble of the main claim. Such spreaders, as a result of being used mainly for spreading manure and granular fertilizers, are commonly referred to in the field as "fertilizer spreaders". Technological background

[0005] Centrifugal fertilizer spreaders may be subjected to a double type of problem. The first problem involves the so-called metering effect. The metering effect involves this phenomenon for which, if the flow rate of material dispensed varies, there is a variation of the distribution (for example, with variations of the casting width and / or length) with a resultant variation of the quantity of product which falls on the ground. Fertilizer spreader machines which suffer from the metering effect require different adjustments when varying the dosage to be distributed and this is reflected as poor performance levels in all these automated machines which work with maps for variable metering prescription (or automatic adjustments of metering of the fertilizer in accordance with the different characteristics present locally in the different zones of the ground to be fertilized), as is increasingly required in modern cultivation practices by the precision agricultural techniques. Similarly, the quality of the spreading is heavily compromised when the machine is used with automatic adjustment, with control of the dispensing opening proportional to the advance speed. In centrifugal spreaders, in order to achieve control of the metering effect, it is fundamentally important to achieve control of the point (or, more accurately, the footprint) at which the fertilizer falls onto the spreader disk. Any machine model uses an individual characteristic footprint because the quality of spreading is a combination of different factors: such as, for example, the shape of the spreader disk and the spreading vanes, the speed of rotation of the disks, etc. The shape of the footprint is defined on the metering member and is given by the intersection between the profile of the dispensing opening of the metering member and a metering shutter valve which, by throttling the dispensing opening, controls the metering of the fertilizer which is dispensed by falling on the centrifugal distributor below. The adjustment of the position of the adjusting shutter valve is automated in the machines with proportional adjustment relative to the advance speed and / or, with ones provided with metering adjustment, variable by means of prescription maps or other computerized control.

[0006] The second problem results from the fact that the fertilizer column, during the fall towards the spreader disk, as a result of the occurrences of turbulence generated by the rotation of the disk and the vane arrangement, loses in a random manner the initially imposed shape. This has a negative influence on the control of the metering effect and the quality of the adjustment imposed on the machine. In order to protect the fertilizer column from the turbulence, it is now common to use a pipe (substantially a fertilizer guide) or a barrier which extends from the metering member and descends towards the spreader disk until skimming the casting vane arrangement thereof.

[0007] In order to cause the shape of the fertilizer column to remain as faithful as possible to the one initially defined by the metering member, it is desirable for the fertilizer guide to have in cross-section the same shape and dimensions as the dispensing opening of the metering member under maximum opening conditions. However, it has been found that this design selection hides a disadvantageous trap, that is to say, when the metering shutter valve is actuated so as to open, an aperture or a passage for dispersion of the dispensed material which is determined by the thickness of the shutter valve itself in the free space which is generated between the metering member and the fertilizer guide is formed. Furthermore, if the grain size of the fertilizer has small dimensions, some granules can become introduced through the dispersion passage, causing an undesirable discharge of the granules from the fertilizer guide which alters the precision of the metering and the regularity of broadcast. In order to overcome this disadvantage, a number of constructive cases of fertilizer spreaders use fertilizer guides with greater dimensions than the opening of the metering member (in some cases, it is even open at one side). The use of a fertilizer guide which is greater than the dispensing opening of the metering member reduces or eliminates the possibility that some of the fertilizer may escape therefrom in the section of passage between the metering member and guide, but at the same time causes reduced control of the falling location of the fertilizer on the spreader disk. Therefore, the fertilizer spreader machine is more powerfully subjected both to differences of distribution along the broadcast angle and to the metering effect.

[0008] Centrifugal fertilizer spreaders are often also used to distribute granular toxins, such as slug pellets or rodenticides. Below, use will be made of the term "slug pellets" in order to refer to this type of product. The slug pellets, given the dangerous nature thereof, are distributed in very low dosages, under 10 kg / ha (typically at 3 / 5 kg / ha). The typical dosage of the fertilizers is instead in the order of hundreds of kg / ha; typically, from 100 to 400 kg / ha. Since the metering member of the fertilizer spreaders is specifically configured for spreading fertilizers, by maintaining the portions of the metering member in an unaltered state, it becomes substantially impossible to control in an accurate manner the dosages required for the slug pellets because the opening of the metering member is so great that small movements of the shutter valve for adjusting the metering correspond to great variations of dosages (with respect to the low dosage required). Furthermore, it is practically impossible to control both the metering effect and to use automatic adjustment operations of the metering shutter valve, for example, in order to vary the dosage of product distributed as a function of the advance speed.

[0009] A number of manufacturers have partially overcome the problem by providing, for example, metering shutter valves with multiple openings. With all the dispensing openings open, the spreader is set for distributing fertilizers (or for distribution at high dosages). By intercepting one or more of these openings, it is possible to substantially limit the flow of product dispensed without any risks of blocking the flow itself in order to be able to distribute products at low dosages. Alternatively, there is provision for using metering shutter valves with openings with different cross-sections. By changing from an opening with a greater crosssection to one with a smaller cross-section, the desired effect is obtained of dispensing different quantities of product up to the minimum quantities provided for slug pellets, and the like.

[0010] However, the spreaders which are equipped in this manner lose the possibility of benefitting from automatic adjustments correlated with prescription maps and / or the speed of advance, so much so that these functions have to be deactivated.

[0011] The documents EP2332401 Al and DE102007045905 Al describe a centrifugal spreader and a metering device, respectively.

[0012] The problem addressed by the present invention is to provide a centrifugal spreader for granular materials which is structurally and functionally configured to overcome at least some of the problems set out with reference to the cited prior art. In the context of this problem, an object of the invention is to develop a centrifugal spreader for granular materials, in which the fertilizer guide is constructed so as to minimize the metering effect and at the same time to prevent the dispensed material from being able to elude the control of the falling footprint carried out by the guide itself.

[0013] Another object of the present invention is to provide a spreader for granular products which operates excellently both for high dosages and for extremely low dosages of dispensed product and which at the same time can use all the prerogatives useful for control, including automatic control, of the metering shutter valves.

[0014] Another object of the invention is to eliminate the negative effects resulting from the opening of the dispersion passage when varying the degree of opening of the metering shutter valve.

[0015] Another object of the invention is to provide a spreader which allows optimum control of the metering effect at least for metering the fertilizer and allows a changeover to very low dosages without any substantial modifications.

[0016] Furthermore, an objective of the present invention is to provide a spreader which is suitable for distributing slug pellets without having to modify the metering system for the fertilizer. Another object of the invention is to allow the retrofitting mounting thereof.

[0017] These problems are solved and these objects are achieved by the invention by means of a centrifugal spreader for granular materials including at least some of the features mentioned in the appended claims.

[0018] Description of the invention

[0019] According to an important aspect of the invention, a centrifugal spreader for granular materials comprises at least one metering member which has a dispensing opening which can preferably be throttled. Preferably, there are provided adjustment means for adjusting the throttling of the dispensing opening so as to vary the flow rate of material to be spread which is supplied by falling to at least one corresponding centrifugal distributor. Preferably, the spreader of this invention further includes a guide which is interposed between the dispensing opening and the distributor for conveying the material which is dispensed by the metering member on the centrifugal distributor. In a preferred version of the invention, the guide comprises a main channel which extends between a position directly below the throttling means and a falling zone on the distributor.

[0020] These features allow a reduction and at most elimination of the ventilation effect resulting from the centrifugal distributor. If the geometry of the dispensing opening and of the adjustment means is selected adequately, the metering effect of the spreader is reduced similarly, up to being eliminated.

[0021] According to a preferred feature of the invention, the spreader comprises an additional throttling member which is associated with the guide in order to further throttle upstream or downstream of the dispensing opening the material flow which is dispensed from the dispensing opening towards the guide. Preferably, the additional throttling member is housed between the guide and the adjustment means.

[0022] Preferably, the additional throttling member is mounted on the guide.

[0023] Preferably, the additional throttling member is configured to be mountable on the guide so as to be integrated in the spreader.

[0024] These features allow the additional throttling member to be integrated in the spreader and further make the additional throttling member mountable on spreaders according to a retrofitting logic.

[0025] Preferably, the throttling member is housed between the guide and the adjustment means.

[0026] Preferably, the throttling member comprises a third shutter valve which has a first throttling opening and at least one second throttling opening. This feature allows the material supply to be throttled effectively.

[0027] Preferably, the throttling member is slidingly movable on the guide. Preferably, the throttling member is movable so as to have in correspondence of the dispensing opening alternately the first throttling opening or the second throttling opening.

[0028] Preferably, the second opening has a passage aperture with an extent less than the passage aperture of the first opening. This feature implicitly allows versatility in throttling, thereby providing different adjustment modes.

[0029] Preferably, the first opening has dimensions which are at least equal to the dispensing opening. Preferably, the first throttling opening is formed so as not to interfere with the passage of material through the dispensing opening. This feature allows the spreader to be provided with the throttling member while not further adjusting the dispensing of material. Preferably, the guide includes a flange with which the guide is mounted on the metering member. Preferably, the throttling member is guided on the flange of the guide. These features allow the throttling member to be suitably housed in such a manner that it is reliably movable in order to have the first or second opening on the guide.

[0030] Preferably, the second throttling opening has a formation with an increasing cross-section with the increasing progression of the throttling adjustment resulting from the adjustment means.

[0031] Preferably, the second throttling opening has an ovoid formation with the greater axis orientated coherently with a movement direction of the throttling member. These formations of the second opening allow the throttling of the material to be suitably adjusted.

[0032] Preferably, the adjustment means are interposed between the dispensing opening and the guide potentially causing the opening of a dispersion passage for the material during the throttled dispensing of the material.

[0033] Preferably, the guide comprises at least one secondary channel which is provided radially externally with respect to the main channel and which opens inside the main channel. Preferably, the secondary channel is provided to collect material which is dispensed from the dispensing opening of the metering member and which is discharged out of the main channel into the dispersion passage in order to convey it into the main channel.

[0034] Preferably, the first throttling opening is at least partially surrounded by additional openings which are provided for collecting material which is dispersed in the dispersion passage and to convey it into at least one secondary channel of the guide. Preferably, the second throttling opening is at least partially surrounded by additional openings which are provided for collecting material which is dispersed in the dispersion passage and to convey it into at least one secondary channel of the guide.

[0035] These features prevent the dispersion of material and instead allow it all to be conveyed efficiently into the guide because it is supplied to the centrifugal distributor, thereby maximizing the output of the material inserted into the metering member of the spreader.

[0036] Preferably, the flange of the guide comprises peripheral shoulders.

[0037] Preferably, the third shutter valve has a substantially rectangular outline.

[0038] Preferably, the third shutter valve is slidingly guided between the shoulders of the guide. These features allow the throttling member to be reliably guided on the guide so as to efficiently throttle the dispensing of material.

[0039] Preferably, the spreader comprises locking means which can be associated with the shoulders in order to block the throttling member in predefined operating positions. These features allow the throttling member to be secured to the guide so as to keep the positioning of the first opening and the second opening unchanged with respect to the same guide, therefore keeping constant the predefined throttling of material.

[0040] Preferably, the third shutter valve takes up a throttled position, in which the second opening is in correspondence with the dispensing opening and preferably takes up a non-throttled position, in which the first opening is in correspondence with the dispensing opening.

[0041] Preferably, the third shutter valve is actuated by means of an actuator, preferably of the electromechanical type or with manual actuation.

[0042] Brief description of the Figures The features and advantages of the invention will be better appreciated from the following detailed description of a preferred though non-exclusive embodiment thereof, which is illustrated by way of non-limiting example with reference to the appended drawings, in which:

[0043] - Figure 1 is a plan view of the spreader to which the invention relates;

[0044] - Figure 2 is a side view of the spreader to which the invention relates;

[0045] - Figures 2a and 2b show the spreader of Figure 2, in which a local cross-section and an enlargement of the same local cross-section have been depicted;

[0046] - Figures 3 and 4 illustrate a perspective view and a partially sectioned side view of a detail of the spreader of Figure 1, respectively;

[0047] - Figure 5 is a perspective, exploded view of the content of Figure 3;

[0048] - Figure 6 is a perspective, exploded view of one embodiment of the invention being considered;

[0049] - Figures 7 and 8 show different configurations of the embodiment illustrated in Figure 6, respectively.

[0050] Preferred embodiment of the invention

[0051] In the Figures, there is generally designated 1 a centrifugal spreader for granular materials. The spreader in the configuration for use is generally combined with a hopper, a tank or other container for the material to be spread, which is known per se, and comprises a metering member 2 which tapers towards the bottom and which terminates as a base 3, in which a dispensing opening 4 is provided. An agitator 5 can be provided to facilitate the descent of the material through the dispensing opening 4. In the example illustrated (according to one of the possible configurations), this agitator 5 preferably comprises a star-like rotor 6 which is rotated by means of a shaft 7. It may be noted that the dispensing opening 4 is substantially circular and is formed by means of a peculiar profile 8 near the side adjacent to the agitator 5. It cooperates with adjustment means 9, preferably of the shutter valve type, comprising a metering shutter valve 9A which is formed with an otherwise peculiar counter- profile 10 which is intended to define, with the profile 8, an outlet footprint 11 for the product, or the material, with adjustable dimensions and formations. The interaction between the profile 8 of the dispensing opening 4 and the counter-profile 10 of the metering shutter valve 9A allows a reduction, up to elimination where applicable, of the metering effect which is generated by the spreader 1 when the discharge footprint 11 of the material is varied.

[0052] The flow rate of the material to be spread which is introduced into the metering member 2 is supplied by falling onto at least one corresponding centrifugal distributor 12, for example, of the disk type 13, which is provided with a casting vane arrangement 14.

[0053] Since the centrifugal distributor 12, which is rotated rapidly about its axis, generates an air flow with a high level of turbulence in the area between the disk 13 and dispensing opening 4, a fertilizer guide 15 or simply guide 15 is used and is applied immediately below the adjustment means 9 in order to direct the flow of material to be spread as close as possible to the distributor 12 without changing, as far as possible, the distribution thereof imposed by the discharge footprint 11.

[0054] A closure shutter valve 9B may be associated with the metering shutter valve 9A of the adjustment means 9, where applicable. The closure shutter valve 9B allows interruptions in the dispensing of material without changing the adjustment of the metering shutter valve 9A. More specifically, the closure shutter valve 9B overlaps with respect to the metering shutter valve 9A.

[0055] The metering shutter valve 9A and the closure shutter valve 9B are preferably controlled independently by means of respective actuators 17, 18. In particular, a first actuator 17 is configured to adjust, where applicable, continuously (according to metered distribution programmes and / or according to the speed of advance of the operating machine) the flow of the material to be spread by modifying the positioning of the metering shutter valve 9A. A second actuator 18 is configured to open and close the closure shutter valve 9B by intercepting the dispensing opening 4 without intervening in the adjustment of the metering shutter valve 9A.

[0056] It may be observed that the adjustment means 9, as a result of using a throttling member with a movable shutter valve of the dispensing opening 4 having a predetermined thickness, in addition to the thickness of the closure shutter valve 9B, where present, bring about a spacing of the guide 15 away from the dispensing opening 4 so that, when the shutter valve(s) is / are opened, this corresponds to simultaneous opening of a dispersion passage 28 of the material dispensed. Conversely, in the absence of the dispersion passage 28, the movement of the adjustment means 9 involves an accumulation of material, which, remaining caught, can cause a blockage of the same adjustment means 9. In the absence of the arrangements provided for by the present invention, the presence of this dispersion passage 28 would involve a loss of material to be distributed outside the fertilizer guide 15 and therefore uncontrolled dispensing and distribution thereof, thereby changing the broadcast precision of the material and the metering effect.

[0057] In order to prevent this, the fertilizer guide 15 comprises a tubular member 19 having a first end which is provided with a flange 20, with which the same fertilizer guide 15 is fixed under the metering member 2, and a second opposite end, where applicable and preferably provided with a brush-like seal 21, which is flush with the vane arrangement 14. The closure shutter valve 9B and the metering shutter valve 9A are preferably both guided between shoulders 50 of the fertilizer guide 15 in a predetermined direction D. Preferably, these shoulders 50 are positioned at opposite sides of the flange 20 of the fertilizer guide 15 so as to slidingly guide the metering shutter valve 9A and closure shutter valve 9B in this direction D.

[0058] A main channel 22 is formed in the member 19 which is preferably delimited by an annular element 23 having an identical, or alternatively substantially similar, internal formation to the formation of the dispensing opening 4.

[0059] This annular element 23 is supported by the fertilizer guide 15 by means of a plurality of shoulders 24 which project towards the interior of the main channel 22 and which has at least one and preferably a plurality of openings 29, which are preferably arranged between the shoulders 24 of the guide 15 itself, thereby delimiting at least one corresponding secondary channel 25. Each secondary channel 25 allows the dispersed material to be collected and to be conveyed into the same main channel 22. Preferably, a plurality of secondary channels 25 surround the main channel 22. Each secondary channel 25 is formed so as to taper towards the main channel 22.

[0060] The connection between the annular element 23 and the top of the shoulders 24 is preferably brought about in an interlocking manner by means of respective connection counter-members 26, such as, for example, extension pieces, which are received in corresponding connection members 27 of the same annular element 23. Other types of connection (form-fitting connection or other types) are suitable for the same result. There is included in the same invention the hypothesis of reducing the number of shoulders 24 so as to minimize the resultant number of secondary channels 25 in favour of a single secondary channel 25 which is substantially continuous and which surrounds the main channel 22, extending over the entire circumferential section of the guide 15. Preferably, the openings are positioned on the annular element 23 so as to correspond to the outlet of the dispersion passage(s) 28 in such a manner that the dispersed material is completely conveyed into the main channel 22, completely eliminating the dispersion of the granular material but without changing in any manner the geometry of the dispensing opening 4 and / or the outlet footprint 11 of the material dispensed.

[0061] Preferably, in order to move from the high dosages, which are required, for example, for fertilizer products, to the low or extremely low dosages, which are required, for example, for slug pellets, there is provided a throttling member 40 which can be associated with the fertilizer guide 15. More specifically, the throttling member 40 is mounted on the fertilizer guide 15 so as to be effectively integrated in the centrifugal spreader 1. In particular, this throttling member 40 is configured to further throttle upstream or downstream of the dispensing opening 4 the flow which is dispensed therefrom towards the above-mentioned fertilizer guide 15.

[0062] Preferably, the throttling member 40 comprises a third shutter valve 41 in which two or more throttling openings 42, 43 are formed. The throttling member 40 is preferably slidingly movable in the direction D parallel with and overlapping with the metering shutter valve 9A and closure shutter valve 9B. The first throttling opening 42 preferably has a cross-section identical to or greater than the dispensing opening 4 and is substantially configured not to interfere with the flow of material to be dispensed when it overlaps the dispensing opening 4.

[0063] The second throttling opening 43 has an extent less than the first throttling opening 42 so as to restrict the free aperture at the inlet to the fertilizer guide 15, consequently limiting the quantity of material dispensed.

[0064] The third shutter valve 41 preferably has a rectangular outline and is slidingly guided between the shoulders 50. Preferably, the third shutter valve 41 can be locked in a predefined operative position by way of locking means 51. Preferably, the locking means 51 can be associated with the shoulders 50 or the flange 20 of the fertilizer guide 15, on which all the above-mentioned shutter valves are guided.

[0065] The third shutter valve 41 has at one end thereof at least a first shoulder 45 which is formed so as, during use, to abut the flange 20 of the fertilizer guide 15 and to prevent the further sliding of the same third shutter valve 41, thereby defining a first limit. Preferably, the third shutter valve 41 has at least one second shoulder 46 in the region of a second end thereof, preferably opposite the first shoulder 45. In particular, the second shoulder 46 is formed so as, during use, to prevent the further sliding of the third shutter valve 41, thereby defining a second limit. Preferably, this third shutter valve 41 is positioned on the flange 20 of the fertilizer guide 15 so as to take up alternately a throttled position P, in which the second throttling opening 43 is located in the region of the dispensing opening 4, that is to say, in which the dispensing of the material is further throttled, and a non-throttled position N, that is to say, in which the first throttling opening 42 is located in the region of the dispensing opening 4, that is to say, in which the dispensing of material is not influenced by the throttling member 40. Preferably, the first and second throttling openings 42, 43 are substantially aligned along the member of the third shutter valve 41 and particularly in the direction D.

[0066] The second throttling opening 43 has such a shape that, as the aperture of the dispensing opening 4 increases, as a result of the effect of the sliding of the metering shutter valve 9A, the free aperture provided by the second throttling opening 43 increases proportionally.

[0067] Preferably, the second throttling opening 43 has an ovoid shape, in particular has the greater axis orientated in the direction D.

[0068] Both openings 42, 43 are preferably at least partially surrounded by additional openings 47 having, in the two operative positions of the third shutter valve 41, the same arrangement and function as the openings 29 of the annular element 23 of the fertilizer guide 15, or the collection of the dispersed material in the dispersion passage 28 in order to convey it into the fertilizer guide 15.

[0069] The movement of the third shutter valve 41 can be both of the manual type and of the automatic type, for example, by means of an additional actuator, which is not illustrated in the relevant Figures.

[0070] It will be understood that the third shutter valve 41 allows only the different positions, in which the throttling openings 42, 43 are located in correspondence with the dispensing opening 4. At the same time, however, the adjustment of the metering resulting from the movement of the adjustment means 9 remains clearly effective, for example, by means of the first shutter valve 9A, which can therefore be brought about automatically. This automation can be carried out according to the programmed control of the first actuator 17, consequently the spreader 1 according to the invention is suitable for the automatic adjustment of spreading both with the reduced metering imposed for slug pellets and for the metering necessary for fertilizers, for example. Among the main advantages of the invention, the following ones are particularly important:

[0071] - minimizing or eliminating the metering effect for metering fertilizer;

[0072] - minimizing or eliminating the metering effect at least for metering slug pellets;

[0073] - avoiding the uncontrolled dispensing of material from the spreader; - avoiding the dispersion of material in the dispersion passage during the throttling of the dispensing of material;

[0074] - forming a spreader which is suitable for alternately distributing both the slug pellets and the fertilizer without modifying the metering system of the fertilizer and which can further be installed by retrofitting; - forming a spreader which can be controlled suitably, even where applicable in an automated manner, both for extremely low and for extremely high dosages of dispensed material.

Claims

Patent claims1. Centrifugal spreader (1) for granular materials, comprising at least one metering member (2) which has a dispensing opening (4) which can be throttled, adjustment means (9) for adjusting the throttling of said dispensing opening (4) so as to vary the flow rate of material to be spread which is supplied by falling to at least one corresponding centrifugal distributor (12) and a guide (15) which is interposed between said dispensing opening (4) of said metering member (2) and said centrifugal distributor (12) for conveying the material which is dispensed by said metering member (2) on said centrifugal distributor (12), said guide (15) including a main channel (22) which extends between said adjustment means (9) and a material falling zone on said centrifugal distributor (12), characterized in that it comprises an additional throttling member (40) which is associated with said guide (15) in order to further throttle upstream or downstream of said dispensing opening (4) the material flow which is dispensed from said dispensing opening (4) towards said guide (15).

2. Centrifugal spreader (1) according to claim 1, wherein said additional throttling member (40) is mounted on said guide (15) so as to be integrated in said centrifugal spreader (1).

3. Centrifugal spreader (1) according to claim 1 or 2, wherein said throttling member (40) is housed between said guide (15) and said adjustment means (9).

4. Centrifugal spreader (1) according to one or more of the preceding claims, wherein said throttling member (40) comprises a third shutter valve (41) which has a first throttling opening (42) and at least one second throttling opening(43).

5. Centrifugal spreader (1) according to claim 4, wherein said throttling member (40) is slidingly movable on said guide (15) so as to have in correspondence of said dispensing opening (4) alternately said first throttling opening (42) or said second throttling opening (43).

6. Centrifugal spreader (1) according to claim 4, wherein said second throttling opening (43) has a passage aperture with an extent less than the passage aperture of said first throttling opening (42).

7. Centrifugal spreader (1) according to any one of claims 4 to 6, wherein said first throttling opening (42) has dimensions which are at least equal to said dispensing opening (4), said first throttling opening (42) being formed so as not to interfere with the passage of material through said dispensing opening (4).

8. Centrifugal spreader (1) according to one or more of the preceding claims, wherein said guide (15) includes a flange (20) with which said guide (15) is mounted on said metering member (2), said throttling member (40) being guided on said flange (20) of said guide (15).

9. Centrifugal spreader (1) according to any one of claims 4 to 8, wherein said second throttling opening (43) has a shape with an increasing cross-section with the increasing progression of the throttling adjustment resulting from said adjustment means (9).

10. Centrifugal spreader (1) according to any one of claims 4 to 9, wherein said second throttling opening (43) has an ovoid shape with the greater axis orientated coherently with a movement direction (D) of said throttling member (40).

11. Centrifugal spreader (1) according to one or more of the preceding claims,wherein said adjustment means (9) are interposed between said dispensing opening (4) and said guide (15) potentially causing the opening of a dispersion passage (28) for the material during the throttling of said dispensing opening (4), said guide (15) comprising at least one secondary channel (25) which is provided radially externally with respect to said main channel (22) and which opens inside said main channel (22), said secondary channel (25) being provided to collect material which is dispensed from said dispensing opening (4) of said metering member (2) and which is discharged out of said main channel (22) into said dispersion passage (28) in order to convey it into said main channel (22).

12. Centrifugal spreader (1) according to claim 11, wherein said first throttling opening (42) and said second throttling opening (43) are at least partially surrounded by additional openings (47) which are provided for collecting dispersed material in said dispersion passage (28) and to convey it into said at least one secondary channel (25) of said guide (15).

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