Abstract:
A volumetric metering device for the metered delivery of granular and powdery materials, particularly for machines for distributing such materials. The device comprises a housing formed in one piece of plastic material, a metering member which is supported rotatably in the housing, can be handled individually, and includes a plurality of metering wheels mounted on a shaft and clamped in a group between two flanges, a selective drive-transmission interposed between the wheels and the shaft, a scraper for cleaning the wheels in motion and anchoring the idle wheels, and a feeler device which is held at a distance from the metering member with resilient preloading.

Description:
TECHNICAL FIELD  
       [0001]     The subject of the present invention is a metering device for the metered delivery of granular and powdery materials, particularly for machines for distributing the said materials.  
       TECHNOLOGICAL BACKGROUND  
       [0002]     Volumetric metering devices are used widely in many different technical fields in which there is a need to deliver a substantially continuous and measured flow of material over time. For example, the technical field of agricultural sowing machines with pneumatic seed-transportation is typical; in these machines it is known to provide a seed-loading hopper at the base of which a metering device, generally of the volumetric type with blades, is fitted and supplies metered quantities of seeds into a Venturi duct by which the seeds are admitted to an air-flow and transported to the sowing drills.  
         [0003]     The particular and preferred application of the invention is in all cases in which it is necessary to vary the flow-rate delivered, possibly within a fairly large range of values.  
         [0004]     Typical metering devices formed in accordance with the prior art are described, for example, in EP 0702890, EP0606541, EP 0471155, and U.S. Pat. No. 6,138,591.  
         [0005]     Conventional metering devices normally comprise a box-like structure in which a bladed metering member is supported rotatably and cooperates with a flow-restricting device for regulating the flow-rate delivered. In one example, the restricting device comprises a jacket movable axially in adjustable manner relative to the rotor of the distributor so as to cover a portion of the set of blades in order to reduce the overall capacity of the cells available. Alternatively, the rate of rotation of the metering member may be varied, or the capacity of the cells may be varied.  
         [0006]     A first problem resulting from the known structure of conventional distributors is that they do not permit large adjustments of flow-rate whilst maintaining constant regulation of the metering for each adjustment. In fact there are critical speeds of the metering member beyond which its reliability is reduced.  
         [0007]     A second problem typical of known structures is that they comprise a plurality of parts which have to be assembled by means of connections, screws, flanges etc. This philosophy is rather unsuitable for agricultural machines for which many adjustments have to be performed in the field and the consequent need to remove various parts may lead to their loss, making reassembly impossible.  
         [0008]     A further problem characteristic of metering devices is that they are subject to irremediable damage, or at least to blockage of the metering member, when foreign bodies of considerable size reach its rotor. In the absence of a timely indication of this situation, particularly during sowing, it is possible, completely unwittingly, to sow whole fields unevenly or not at all.  
       DESCRIPTION OF THE INVENTION  
       [0009]     These problems and yet others which will become clearer from the following description are addressed and solved by the invention by means of a metering device formed in accordance with the appended claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The characteristics and the advantages of the invention will become clearer from the detailed description of a preferred but not exclusive embodiment described by way of non-limiting example, with reference to the appended drawings, in which:  
         [0011]      FIG. 1  is a schematic view showing, in section, the basic components of a machine for distributing granular materials,  
         [0012]      FIG. 2  is an exploded, perspective view of a delivery device formed in accordance with the present invention,  
         [0013]      FIG. 3  and  FIG. 4  are exploded views of respective variants of a detail of the device of  FIG. 2 ,  
         [0014]      FIGS. 5, 6  and  7  are perspective views of the device of  FIG. 2  in the assembled condition, taken from different angles,  
         [0015]      FIGS. 8 and 9  are perspective views of the device of  FIG. 2  in an only partially assembled condition, taken from different angles,  
         [0016]      FIG. 10  is a perspective view of a detail of the device of  FIG. 2 , on an enlarged scale, and  
         [0017]      FIG. 11  is a side view of a further detail of the device of  FIG. 2 .  
     
    
     PREFERRED EMBODIMENT OF THE INVENTION  
       [0018]     With reference to  FIG. 1 , a machine for distributing granular materials, usable both for sowing seeds and for spreading manure, disinfectants etc., is generally indicated  1 . The machine  1  comprises, basically, one or more hoppers  2  for holding the material to be spread, a blower  3  which delivers an air-flow under pressure to an air injector  4 , a metering device  5  which supplies metered quantities of the material present in the hopper into the air-flow generated by the blower  3 , and a distributor  6  which distributes the mixed flow of air and material transported thereby towards distribution ducts  7 .  
         [0019]     The metering device  5  can advantageously be constructed in accordance with one or more of the teachings of the present invention and is shown in detail in  FIG. 2  and the subsequent figures.  
         [0020]     The device comprises a housing  10  which, by virtue of the provisions of the invention, can advantageously be constructed in a single piece by moulding of plastics material. The housing  10  comprises a first, upper opening  11  which is open towards the hopper  2 , a second, rear opening  12 , closed in an openable manner by a removable door  14 , and an opposed, third opening  15  which admits the granular material to the region of the air injector. The housing is closed at the bottom by a feeler member  16  which will be described further below.  
         [0021]     The housing  10  further comprises opposed side walls  17  having two circular and coaxial through-holes  18 . The holes serve for housing a metering member, generally indicated  20 , in the housing  10 .  
         [0022]     The metering member  20  comprises a shaft  21  of polygonal, preferably square, cross-section, having, at one end, a joint  22  by means of which it can be coupled for rotation with a drive shaft (not shown) and, at the other, opposite end, a threaded shank  23  onto which a hand wheel  24  is screwed with the interposition of a washer  25 . The assembly serves to clamp to the shaft  21  a plurality of metering wheels  26 , included in a group between two flanges  27  and intercalated with discs  28 .  
         [0023]     The flanges  27  are identical to one another and each has two external tracks  29   a ,  29   b  which serve to support the metering member in the housing  10  rotatably but with axial restraint. Support is achieved by means of three or more bearings  30   a ,  30   b ,  30   c , the outer portions of which are in rolling contact with one or other of the tracks  29   a ,  29   b . The axial restraint is not actually necessary for the operation of the device since the shaft  21  is itself fixed axially relative to the housing as a result of its connection to the drive shaft by means of the joint  22 . However, to prevent the metering member  20  from accidentally coming out of the housing  10  when the device is released from the drive shaft, the tracks  29   a ,  29   b  have different diameters (the track  29   a , closer to the side wall of the housing, has a larger diameter) and one bearing  30   a  is fixed to the housing  10  removably by means of the hand wheel  32  and is engaged on the track  29   b  so that the shoulder existing between the two tracks performs the desired axial restraint. In order to remove the metering member from the housing, the hand wheel  32  is slackened, removing the bearing  30   a  and with it the axial restraint preventing the metering member from slipping out.  
         [0024]     Both of the flanges, or at least one of them, may have a ring of axial seats  33  for cores (for examples, screws) cooperating with a proximity detector (not shown) in order to measure the rate of rotation of the metering member  20 .  
         [0025]     Each metering wheel  26  is moulded of plastics material and comprises a plurality of blades  36  which extend radially from a hub  37  having an axial hole  37   a  with a channelled profile in which the channels have a profile which can be coupled with the shaft  21  and the number of channels is a multiple of the number of sides of the shaft so as to permit different angular positionings of the wheels  26  on the shaft  21 . The wheels can thus be mounted in a manner such that they are offset angularly relative to one another, improving the uniformity of the output.  
         [0026]     Both to take account of this angular offset and to strengthen the blades at their free ends, axial appendages  38  are provided thereon and are housed in corresponding holes  39  in the discs  28 . The discs  28  have circular holes and are not otherwise driven by the shaft  21 .  
         [0027]     The wheels  26  are interchangeable with second wheels  26   a  of different volumetric capacity or even with third wheels  40  of low volumetric capacity, which can also be mounted on the shaft  21  with the interposition of a release mechanism  41  (see  FIGS. 3 and 4 ). One or more of the third wheels  40  can thus be disconnected from the drive of the shaft simply by being turned through 180°. In one direction, the mechanism  41  in fact brings about driving of the wheel  40  together with the shaft  21 , whereas in the opposite direction, the mechanism  41  is disengaged from the shaft  21 , rendering the wheel  40  idle. Moreover, for intermediate capacities, the first and second wheels  26 ,  26   a , may be combined in the metering member  20 , by being arranged alternately in the group of wheels.  
         [0028]     A particular problem which is solved by the invention lies in the fact that some minute seeds with a high oil content (typically rape seeds) tend to release greasy substances into the cells of the metering wheels (and into the metering device in general), changing its capacity (to the extent of reducing it to zero). This specific problem has been solved by the invention by means of a special scraper device  50  which is mounted downstream of the region in which the seeds fall. The scraper  50  comprises a shaft  50   a  on which bow-shaped metal scraper members  51 , for example, of harmonic steel, are mounted; the number of scraper members  51  corresponds to the number of wheels  40 . Each scraper member has a crosspiece  52  which can follow the profiles of the cells, deforming the corresponding bow resiliently whilst the wheel  40  rotates. The shaft  50   a  is in turn rotatable on the housing between two positions in which the scraper members are disengaged from the wheels or, conversely, are engaged in contact therewith, respectively. Oily residues which tend to stick to the seeds and to the ever-present dust, are thus removed and fall into the pneumatic seed-conveyor duct in order to be removed from the device  5 .  
         [0029]     Again, with oily seeds, in spite of the provision of release mechanisms, one or more of the wheels which are intended to be rendered idle by being turned around on the shaft  21  may nevertheless be rotated as a result of the internal friction which is increased by the presence of residues of dirt. To prevent this occurring, the wheels  40  according to the present invention have, in one or more of the cells formed in their surfaces between adjacent blades, respective tooth-like formations  54  which, in one direction of rotation, offer the crosspieces  52  of the scraper members an inclined rear face  55  on which the crosspiece  52  does not grip whereas, in the other direction of rotation, they offer the crosspiece  42  a substantially radial leading face with which the crosspiece  52  engages, preventing further driving of the wheel  40 . An example of this function relates to the central wheel of  FIG. 10 .  
         [0030]     The ability to release the scrapers from the wheels  40  when they are not required considerably reduces wear of the scrapers, maintaining their effective life.  
         [0031]     A further advantageous aspect of the invention lies in the structure and functional capacity of the feeler member  16 . In known solutions, this member is generally constituted by a pivoting scraper blade provided with a resilient rubber lip. The main disadvantages resulting from this structure are connected with the fact that, with variations in the rate of rotation of the metering member, the rubber lip deforms, varying the flow-rate of the device in a non-predetermined manner. Moreover, the passage of any foreign body (a stone or the like) can block its pivoting in the open position, with a consequent unexpected change in the metering.  
         [0032]     The feeler member  16  according to the invention comprises a plurality of individual feeler elements  60 , each having a first end engaged on a shaft  61  and each carrying, at its opposite end, a fork  62  which houses a further shaft  63  with predetermined clearance. The fork prong  66  facing the metering member  20  carries a resilient lip  67 . Both of the shafts  61 ,  63  are supported between the side walls  17  of the housing  10 .  
         [0033]     The feeler elements  60  are spaced apart by fixed plate-shaped separators  68 , which are also articulated on the shaft  61  at one end and engage the shaft  63  with their opposite ends, but without the ability to pivot about the shafts.  
         [0034]     In the region of the fork  62 , there are resilient preloading means, each including a helical spring  64  and a respective stay  65 , which urge the respective feeler element  60  towards the corresponding metering wheel. However, the feeler element is kept spaced therefrom by the interaction of the corresponding prong of the fork  62  with the shaft  63 . Alternatively, similar resilient preloading means are arranged to be active at the opposite end of each feeler element. It is thus possible to apply to the elements  60  a predetermined resilient preloading, preferably of the order of about 1.5 kg, without this leading to compression of the lip  67  against the metering member which, in conventional systems, is a potential cause of rupture of the seeds distributed. On the other hand, the feeler elements can perform oscillations about the shaft  61  which are limited by the other prong of the fork  62  so as to prevent the feeler member from opening completely, significantly altering the distribution parameters. This precaution is augmented by the provision of individual and independent feeler elements for each wheel.  
         [0035]     With these means for limiting the pivoting of the feeler member, breakages f the feeler elements could occur should foreign bodies of dimensions larger than he maximum opening between the feeler elements and the respective wheels pass through the metering member. To prevent this, according to a further characteristic of the invention, each separator  68  is arranged to have a nib  69  of a shape and size such as to alter the angle of introduction between the feelers and the metering member  20  so that foreign bodies arriving in the introduction opening between the feelers and the metering body are “rejected” by virtue of the increased amplitude of the angle of introduction as defined above and are prevented from entering the introduction opening. By way of indication, the angle of introduction as varied by the provision of the nibs  68  is about 80°.  
         [0036]     According to a further characteristic of the invention, flow separator means  70  may be arranged in the region of the opening  15  for admitting the granular material into the air-flow which is responsible for its transportation. These separator means  70  are of the type comprising a fixed plate supported, by means of notches  71 , on shafts  72 ,  73  extending between the side walls  17  of the housing  10 . The shaft  72  also serves to support respective surfaces for collecting the seed and sending it to the air-injection duct  4 .  
         [0037]     On the side facing the metering member, the separator plate  70  has an arcuate profile  74  complementary with the outer surface of a toothless wheel  75  which is fitted centrally between the metering wheels. It is thus possible, with a single metering device, to supply two distributors and respective blowers separately, in fact doubling the capacity of the distributing machine.  
         [0038]     According to an additional characteristic of the invention, second separator means  76  may be disposed in the housing, upstream of the metering member  20 , so as to separate, not only at the output but also at the input, products which may optionally be different and which can be metered by a single metering device. The second separator means  76  comprise a fixed plate, also provided with an arcuate profile  77  complementary with the surface of the toothless wheel  75 , and having teeth  78  for engagement on a plate  79  which is equipped with two doors  80  and can replace the door  14  when this arrangement is selected. Amongst the advantages conferred by this technical solution is the fact that it is possible to distribute different products through the right-hand and left-hand sides of the same metering device. For example, it is possible to construct sowing machines with double seed-loading hoppers and a single metering device suitable, for example, for sowing alternating bands of male and female plants for the production of selected hybrids. That is, it is possible to distribute different products simultaneously, optionally with different metering, adjustable in dependence on the type of metering wheels used for the right-hand and left-hand sides.  
         [0039]     Finally, a stirrer  81  is provided, supported rotatably between the side walls  17  of the housing  10  and rotated by the joint  22 , by means of a belt transmission  82 .  
         [0040]     The metering device of the present invention thus achieves the objects indicated, at the same time offering many advantages over the prior art, amongst which is greater ease of handling during operations to assemble and dismantle the individual components.