Volumetric metering device for the metered delivery of granular and powdery materials particulary for machines for distributing such materials

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.

TECHNICAL FIELD

The subject of the present invention is a metering device for the metered delivery of granular and powdery materials, particularly for machines for distributing such materials.

TECHNOLOGICAL BACKGROUND

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.

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.

Typical metering devices formed in accordance with the prior art are described, for example, in EP 0702890, EP 0606541, EP 0471155, and U.S. Pat. No. 6,138,591.

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 an 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.

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.

A second problem typical of known structures is that they comprise a plurality of parts which have to be assembled using connections, screws, flanges, etc. This construction 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 re-assembly impossible.

A further problem characteristic of conventional 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 the 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.

An object of the present invention is to provide an improved volumetric metering device that solves one or more of the problems identified above.

SUMMARY OF THE INVENTION

These problems and yet others which will become clearer from the following description are addressed and solved by the subject invention. In one embodiment, the invention is a volumetric metering device for the metered delivery of granular and powdery materials, particularly for machines for distributing such materials, comprising a housing and a metering member supported rotatably in the housing, characterized in that the housing is formed in a single piece. In another embodiment, the metering member comprises at least one metering wheel clamped between a pair of flanges, the housing comprising juxtaposed openings at least one of which has dimensions such as to allow the metering member, complete with the at least one wheel and the flanges, to pass from and towards the housing, at least one of the flanges being arranged to close the respective opening when the metering member is fitted in the operative position in the housing, and constituting a mechanism for the rotatable support of the metering member in the housing.

In another embodiment, the metering member includes a plurality of metering wheels which are structurally independent of one another and are interposed in a group between a pair of flanges, and a shaft acting as a tie between the flanges in order to clamp in a group the flanges and the metering wheels interposed between them, to constitute a unit which can be handled individually. In yet another embodiment of the present invention, the metering member carries a plurality of metering wheels having blades and being clamped together in a group, characterized in that the blades have appendages restraining the blades of one wheel on the blades of the adjacent wheel.

The metering member of a further embodiment of the present invention has metering wheels clamped in a group and keyed to a common drive-transmission shaft. A selective drive-transmission mechanism is interposed between the wheels and the shaft in order to exclude the wheels from driving by the shaft or, conversely, to connect the wheels for driving by the shaft.

Pursuant to another embodiment, the invention is a volumetric metering device for the metered delivery of granular and powdery materials, particularly for machines for distributing such materials, comprising a housing, a metering member supported rotatably in the housing, and a feeler device mounted in the housing and active in the manner of a scraper blade with a lip thereof operative on the metering member. A restraining mechanism is active on the feeler device in order to keep it a predetermined distance from the metering member. A resilient preloading mechanism is active on the feeler device in order to press its operative lip towards the metering member with a predetermined preload. Whether it includes a restraining mechanism and a resilient preloading mechanism or not, the volumetric metering device may be modified to include an element for altering locally the angle of introduction between the feeler device and the metering member; the element is associated with the feeler device and located immediately upstream of the operative lip.

PREFERRED EMBODIMENT OF THE INVENTION

With reference toFIG. 1, a machine for distributing granular materials, useful both for sowing seeds and for spreading manure, disinfectants, and the like, is generally indicated by the number1. The machine1comprises, basically, one or more hoppers2for holding the material to be spread, a blower3which delivers an air-flow under pressure to an air injector4, a metering device5which supplies metered quantities of the material present in the hopper into the air-flow generated by the blower3, and a distributor6which distributes the mixed flow of air and material transported thereby towards distribution ducts7.

The metering device5can advantageously be constructed in accordance with one or more of the teachings of the present invention and is shown in detail inFIG. 2and the subsequent figures.

The metering device5comprises a housing10which, by virtue of the provisions of the invention, can advantageously be constructed in a single piece (i.e., as one complete, integral, and monolithic unit) by molding plastic material. The housing10comprises a first, upper opening11which is open towards the hopper2; a second, rear opening12, closed in an openable manner by a removable door14; and an opposed, third opening15which admits the granular material to the region of the air injector4. The housing10is closed at the bottom by a feeler member16which will be described further below.

The housing10further comprises opposed side walls17having two circular and coaxial through-holes18. The holes18serve for housing a metering member, generally indicated20, in the housing10.

The metering member20comprises a shaft21of polygonal, preferably square, cross-section, having, at one end, a joint22coupling the shaft21for rotation with a drive shaft (not shown) and, at the other, opposite end, a threaded shank23onto which a hand wheel24is screwed with the interposition of a washer25. The assembly serves to clamp to the shaft21a plurality of metering wheels26, included in a group between two flanges27and intercalated with discs28.

The flanges27are identical to one another and each has two external tracks29a,29bwhich serve to support the metering member20in the housing10rotatably but with axial restraint. Support is achieved by three or more bearings30a,30b,30c, the outer portions of which are in rolling contact with one or other of the tracks29a,29b. The axial restraint is not actually necessary for the operation of the device since the shaft21is itself fixed axially relative to the housing10as a result of its connection to the drive shaft by the joint22. However, to prevent the metering member20from accidentally coming out of the housing10when the device is released from the drive shaft, the tracks29a,29bhave different diameters (the track29a, closer to the side wall17of the housing10, has a larger diameter) and one bearing30ais fixed to the housing10removably by the hand wheel32and is engaged on the track29bso that the shoulder existing between the two tracks performs the desired axial restraint. In order to remove the metering member20from the housing10, the hand wheel32is slackened, removing the bearing30aand with it the axial restraint preventing the metering member20from slipping out.

Both of the flanges27, or at least one of them, may have a ring of axial seats33for cores (for examples, screws) cooperating with a proximity detector (not shown) in order to measure the rate of rotation of the metering member20.

Each metering wheel26is molded of plastic material and comprises a plurality of blades36which extend radially from a hub37having an axial hole37awith a channelled profile. The channels have a profile which can be coupled with the shaft21and the number of channels is a multiple of the number of sides of the shaft so as to permit different angular positionings of the wheels26on the shaft21. The wheels26can thus be mounted in a manner such that they are offset angularly relative to one another, improving the uniformity of the output.

Both to take account of this angular offset and to strengthen the blades36, at their free ends, axial appendages38are provided on the blades36and are housed in corresponding holes39in the discs28. The discs28have circular holes and are not otherwise driven by the shaft21.

The wheels26are interchangeable with second wheels26aof different volumetric capacity or even with third wheels40of low volumetric capacity, which can also be mounted on the shaft21with the interposition of a release mechanism41(seeFIGS. 3 and 4). One or more of the third wheels40can thus be disconnected from the drive of the shaft simply by being turned through 180°. In one direction, the release mechanism41in fact brings about driving of the third wheel40together with the shaft21whereas, in the opposite direction, the release mechanism41is disengaged from the shaft21, rendering the third wheel40idle. Moreover, for intermediate capacities, the first and second wheels26,26amay be combined in the metering member20by being arranged alternately in the group of wheels.

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 wheels26(and into the metering device5in general), changing its capacity (to the extent of reducing it to zero). This specific problem has been solved by the invention by providing a special scraper device50which is mounted downstream of the region in which the seeds fall. The scraper50comprises a shaft50aon which bow-shaped metal scraper members51, for example, of harmonic steel, are mounted; the number of scraper members51corresponds to the number of third wheels40. Each scraper member51has a crosspiece52which can follow the profiles of the cells, deforming the corresponding bow resiliently whilst the third wheel40rotates. The shaft50ais in turn rotatable on the housing10between two positions in which the scraper members51are 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 metering device5.

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 shaft21may nevertheless be rotated as a result of the internal friction which is increased by the presence of residues of dirt. To prevent this from occurring, the third wheels40according to the present invention have, in one or more of the cells formed in their surfaces between adjacent blades36, respective tooth-like formations54which, in one direction of rotation, offer the crosspieces52of the scraper members51an inclined rear face55on which the crosspiece52does not grip whereas, in the other direction of rotation, they offer the crosspiece52a substantially radial leading face with which the crosspiece52engages, preventing further driving of the third wheel40. An example of this function relates to the central wheel ofFIG. 10.

The ability to release the scrapers50from the third wheels40when they are not required considerably reduces wear of the scrapers50, maintaining their effective life.

A further advantageous aspect of the invention lies in the structure and functional capacity of the feeler member16. 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 member20, the rubber lip deforms, varying the flow-rate of the metering device5in 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.

The feeler member16according to the invention comprises a plurality of individual feeler elements60, each having a first end engaged on a shaft61and each carrying, at its opposite end, a fork62which houses a further shaft63with predetermined clearance. (By “predetermined” is meant a clearance that is chosen, determined, or known beforehand or in advance of operation.) The fork prong66facing the metering member20carries a resilient lip67. Both of the shafts61,63are supported between the side walls17of the housing10.

The feeler elements60are spaced apart by fixed plate-shaped separators68, which are also articulated on the shaft61at one end and engage the shaft63with their opposite ends, but without the ability to pivot about the shafts.

In the region of the fork62, there are resilient preloading mechanisms, each including a helical spring64and a respective stay65, which urge the respective feeler element60towards the corresponding metering wheel. However, the feeler element60is kept spaced therefrom by the interaction of the corresponding prong66of the fork62with the shaft63. Alternatively, similar resilient preloading mechanisms are arranged to be active at the opposite end of each feeler element60. It is thus possible to apply to the feeler elements60a predetermined resilient preloading, preferably of the order of about 1.5 kg, without this leading to compression of the lip67against the metering member20which, in conventional systems, is a potential cause of rupture of the seeds distributed. On the other hand, the feeler elements60can perform oscillations about the shaft61which are limited by the other prong of the fork62so as to prevent the feeler member16from opening completely, significantly altering the distribution parameters. This precaution is augmented by the provision of individual and independent feeler elements60for each wheel.

With these mechanisms for limiting the pivoting of the feeler member16, breakages of the feeler elements60could occur should foreign bodies of dimensions larger than the maximum opening between the feeler elements60and the respective wheels pass through the metering member20. To prevent this, according to a further characteristic of the invention, each separator68is arranged to have a nib69of a shape and size such as to alter the angle of introduction between the feeler elements60and the metering member20so that foreign bodies arriving in the introduction opening between the feeler elements60and the metering member20are “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 nibs69is about 80°.

According to a further characteristic of the invention, a flow separator70may be arranged in the region of the third opening15for admitting the granular material into the air-flow which is responsible for its transportation. The flow separator70is of the type comprising a fixed plate supported, by notches71, on shafts72,73extending between the side walls17of the housing10. The shaft72also supports respective surfaces for collecting the seed and sending it to the air injector4.

On the side facing the metering member20, the flow separator70is a plate with an arcuate profile74complementary with the outer surface of a toothless wheel75which is fitted centrally between the metering wheels26. It is thus possible, with a single metering device5, to supply two distributors6and respective blowers3separately, in fact doubling the capacity of the machine1.

According to an additional characteristic of the invention, a second separator76may be disposed in the housing10, upstream of the metering member20, 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 device5. The second separator76comprises a fixed plate, also provided with an arcuate profile77complementary with the surface of the toothless wheel75, and has teeth78for engagement on a plate79which is equipped with two doors80and can replace the door14when 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 device5. For example, it is possible to construct sowing machines with double seed-loading hoppers and a single metering device5suitable, 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 wheels26used for the right-hand and left-hand sides.

Finally, a stirrer81is provided, supported rotatably between the side walls17of the housing10and rotated by the joint22, by a belt transmission82.

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. Although illustrated and described above with reference to certain specific embodiments, the present invention is nevertheless not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the spirit of the invention.