The present invention relates to a pumping unit.
The invention falls within the sector of fluid dynamic machines and has an application in particular in the sector of agricultural machinery.
It is known to use a pump in various fluid dynamic applications, where the operating concept is to draw a quantity of liquid from a tank and convey it to delivery nozzles or, more generally, to delivery openings in order to favour spraying of liquid from the tank.
For this purpose, fluid dynamic machines using a volumetric pump, generally of the membrane type, are known, said machines having the functions described above. A particular example of these machines are agricultural machines intended for the spraying of agricultural ground and towed by tractors which generally comprise a tank for containing a liquid, for example an aqueous solution of a chemical component, a plurality of spraying nozzles arranged in a position facing the ground and communicating with the tank in order to spray a given quantity of liquid onto the ground, and a volumetric pump which is powered by a power take-off of the tractor and active between the tank and the spraying nozzles in order to generate in the liquid a head sufficient to disperse it through the spraying nozzles.
Spraying of the liquid through the nozzles results in gradual emptying of the tank of said agricultural machines.
Replenishing of the tank with liquid, drawn from a liquid source, is performed by the same volumetric pump.
This fact results in the need to design said pump with larger dimensions so that it is also able to perform the liquid replenishing functions, therefore resulting in high installation costs.
Moreover, owing to the low throughputs which are typical of volumetric pumps, replenishing of the tanks requires a fairly long time-scale.
It is also noted that the liquid in the tank requires frequent mechanical stirring in order to ensure the homogeneity of the solution to be sprayed.
In this case also, the function of stirring the liquid is performed by the volumetric pump via partial recirculation of the product.
The use of these pumps in the agricultural machines described above results in the disadvantage of long down times for replenishing the tank with liquid and moreover a reduction in spraying efficiency due to the partial recirculation of the liquid in order to ensure uniformity thereof. A way of solving the problem is to adopt a second pump, generally of the centrifugal type, in order to perform the functions of replenishing and mechanical stirring of the liquid in the tank.
However, it must be considered that the two pumps perform different functions, i.e. in the specific case the first pump performs the function of delivery of the liquid at a high pressure, while the second pump performs a filling function, in which therefore a high throughput of liquid is required. This has a negative effect on the connection of the pumps to the motor means, owing to the fact that the latter must be powered with different operating parameters.
Consequently it is envisaged installing the usual volumetric pump, powered by the power take-off of the tractor, and the additional installation of the centrifugal pump powered by a combustion engine or a hydraulic motor.
This configuration results in various disadvantages such as high installation and maintenance costs owing to the presence of two pumps and a dedicated motor for powering one of them, large dimensions due to the use of an additional pump and associated power supply motor, and problems of reliability due to the management of two pumps and an additional motor.
To overcome drawbacks mentioned above, in
Nevertheless, this solution shows the important drawback that it cannot allow the two pumps to perform their specific different functions because it is not able to keep the two pumps at their optimum speed of rotation. In fact, the speed variator varies the number of rotations of the second oil pump with respect to the number of rotation of the first pump and so it cannot link two pumps speeds with a stated ratio.
In this situation, the technical task forming the basis of the present invention is to propose a pumping unit which does not possess the abovementioned drawbacks.
The main object of the present invention is to provide a pumping unit which simplifies the connections of the pumps to the motor means intended for operation of the said pumps.
A further object of the invention is to provide a pumping unit which reduces the dimensions of components necessary for connecting the pumps to the respective motor means.
Another object of the invention is to provide a pumping unit which can be easily maintained in view of the fact that said unit operates in agricultural fields and therefore in conditions which are often critical.
These objects, together with others, which will appear more clearly from the following description, are achieved according to the present invention by a pumping unit in accordance with the contents of Claim 1 and/or one or more of the claims dependent thereon.
Further characteristic features and advantages of the invention will appear more clearly from the description of a preferred, but not exclusive embodiment of a pumping unit, in accordance with that explained in detail in the following description and with the aid of the accompanying drawings in which:
The pumping unit 1 can be used in particular in an installation of the type shown in the fluid dynamic diagram according to
In accordance with the front view of
The pumping unit also comprises a second pump 7, having a respective second drive shaft 7a and acting on the tank 2 at least so as to ensure a supply of the liquid to the tank 2 itself. Preferably, the second pump 7 is of the continuous-flow type, in particular of the centrifugal type comprising an impeller 7b and a bell 7c, the second pump 7 having the function of supplying the liquid to the tank 2. It must be remembered in fact that volumetric pumps differ from centrifugal pumps, or more generally from continuous-flow pumps, in that volumetric pumps have operating heads which are higher than centrifugal pumps, but, on the other hand, they are able to cope with a smaller throughput of liquid. It is clear, therefore, that a volumetric pump is better suited than a centrifugal pump for providing the liquid with an optimum head for suction thereof through the delivery nozzles. A delivery pump is, moreover, clearly better for supplying a liquid throughput - even if high - to the inlet of the tank 2.
One of the two drive shafts 6a, 7a, preferably that of the first volumetric pump 6, is directly connected to motor means defined, in the example of agricultural applications, by the power take-off of a tractor not shown in the accompanying figures.
In the case where the pumping unit 1 is housed on an agricultural spraying machine, during operating conditions, the engine of the tractor is always running and therefore the first volumetric pump 6 is always in operation, unless the power take-off of the tractor is disengaged. In order to be able to interrupt the flow of liquid delivered through the delivery openings 4, the first volumetric pump 6 may act on the tank 2 even during recirculation. In detail, in this condition the first pump 6 is active between the tank 2 and the tank 2 itself in order to recirculate a quantity of liquid, drawn from the tank 2, inside it so that it is not necessary to deactivate the first pump 6 in order to interrupt the delivery of the liquid during operation of the tractor, or more generally of the motor means. The recirculation condition is ensured by a first three-way valve "V1" situated downstream of the first pump 6 and communicating selectively with a recirculation pipe "R" leading into the tank 2 or, alternatively with at least one delivery pipe "E" for conveying the liquid to the delivery openings 4, in accordance with the fluid dynamic diagram shown in
Advantageously the pumping unit 1 comprises transmission means 8 which are active between the first drive shaft 6a and the second drive shaft 7a so as to transmit, preferably in a regulated manner, a driving power from the first pump 6 to the second pump 7. The transmission means 8 are rendered necessary by the fact that, as mentioned above, the two pumps 6, 7 have different operating parameters associated with the different design characteristics. In particular, among the characteristic operating parameters of the two pumps 6, 7, most important is the number of revolutions at which each pump 6, 7 is operated. In particular, the first centrifugal pump 6 has an optimum speed of rotation higher than the optimum speed of rotation of the second volumetric pump 7. As a result, the transmission means must ensure at least a suitable reduction - or multiplication - ratio for the number of revolutions of the first drive shaft 6a and the number of revolutions of the second drive shaft 7a.
In the preferred embodiment illustrated in
Advantageously, the second drive shaft 7a has a first end defining the said central hub 9a, while the first drive shaft 6a is operationally active on the planet gears 9c in the manner which will be described below. From the above it can be seen that, since the planet gears 9c have a revolving movement coaxial with the central hub 9a, the two drive shafts 6a, 7a rotate coaxially with each other about a same main axis of rotation "X".
Therefore, the first volumetric pump 6 is of the membrane type and, in the embodiment shown, comprises six valve bodies 10, only two of which are visible in
The transmission means 8 comprise a containing body 14 which is divided into a first portion 14a and a second portion 14b which can be stably joined together by means of first threaded connections 14c.
The first portion 14a and the second portion 14b of the containing body 14 define internally an operating chamber 15 which can be occupied stably by the epicyclic gearing 9. The latter has the ring gear 9b fixed, in particular rigidly joined to the two portions 14a, 14b of the containing body.
The planet gears 9c are rigidly joined together by means of a connecting part 16 which is rotatable about the main axis of rotation "X" and rotatably supports the planet gears 9c by means of respective pins 17 of the connecting part 16. The latter extends from the epicyclic gearing 9 towards the first shaft 6a and is also supported by the third bearing 13. The third bearing 13, therefore, acts as an indirect support for the second drive shaft 7a by means of the connecting part 16 which is connected to the epicyclic gearing 9 to which in turn the second drive shaft 7a is stably connected. The second bearing 12 is housed stably inside a respective seat of the second portion 14b of the containing body 14.
The first portion 14a of the containing body 14 has a terminal portion 18 in the form of a flange which can be stably joined to a respective portion of the first volumetric pump 6, for example by means of second threaded connections 19. The first portion 14a of the containing body 14 and the respective portion of the first pump 6 joined together define internally an operating chamber 20. Reversible engaging means 21 are housed inside this operating chamber 20, active between the epicyclic gearing 9 and the first drive shaft 6a so as to connect the latter together and disengage them from each other in order to interrupt in a controlled manner a flow of power towards the second centrifugal pump 7.
This is useful when the tank 2 has reached a predetermined filling level and it is required to interrupt the supply of other liquid to the tank 2.
In detail, the reversible engaging means comprise an engaging member 22, having a first terminal portion 23 slidably inserted inside the connecting part 16 and rotationally integral with the connecting part 16 itself. This is achieved by coupling the first terminal portion 23 of the engaging member 22 with the connecting part 16 by means of a splined connection, preferably of the telescopic type.
The engaging member 22 has moreover a second terminal portion 24 which is opposite the first terminal portion 23 and can be stably coupled with the first drive shaft 6a in order to form a mechanical connection between the first drive shaft 6a and the second drive shaft 7a, via the connecting part 16 and the epicyclic gearing 9.
In the preferred embodiment shown, the first drive shaft 6a, at its end directed towards the transmission means 8, is integral with a sleeve 25 which defines a hole 26 arranged along the main axis of rotation "X" and able to be engaged by a respective coupling part 27. The latter has a first terminal portion 27a which can be stably inserted inside the sleeve 25 in a stable manner at least with a relative rotational movement of the sleeve 25 and the coupling part 27. This is obtained by providing, inside the sleeve 25, a longitudinal seat 28 which can be engaged by a projection of the coupling part 27, preferably a tongue 29.
Preferably the coupling part 27 is connected to the sleeve 25 so as not to have any freedom of movement relative thereto. This is obtained, for example, by means of a screw which can be inserted in an axial opening 30 of the coupling part 27 and can be stably engaged with a bottom portion 31 of the sleeve 25.
In an alternative embodiment, the sleeve 25 is defined by the said end of the first drive shaft 6a directed towards the transmission means 8.
The coupling part 27 also has a second terminal portion 27b, opposite to the first portion 27a and shaped so as to match substantially the second terminal portion 24 of the engaging member 22, for stably engaging therewith. In particular, the second terminal portion 27b of the coupling part 27 comprises a protuberance 32 which can be engaged inside a respective engaging seat 33 formed in the second terminal portion 24 of the engaging member 22. In particular, the engaging member 22 is movable, along the main axis of rotation "X", between an active position shown in
Advantageously, the transmission means 8 and the second pump 7 may be removed from the pumping unit 1, and the coupling part 27 extracted from the sleeve 25 so that the latter may be connected to a generic motor for separate operation of the first pump 6. In this condition, the first pump 6 may be operated independently of the second pump 7.
Therefore, the form of the sleeve 25, which has a longitudinal seat 28 for the tongue, makes it suitable for coupling in a simple and practical manner with any type of motor since it is known that most of the commercially distributed motors have a shaft with a tongue as the member for transmission of the output movement.
The engaging member 22 has a peripheral seat 34 which extends around the main axis of rotation "X", as shown in
The two flanges 35 allow the engagement of the peripheral seat 34 by a projection 36 of a lever "L". The lever "L" can be operated manually by an operator and is rotatably mounted on the first portion 14a of the containing body 14. The projection 36 is eccentric with respect to an axis of rotation "Y" of the lever "L" and therefore movable about this axis of rotation "Y" with a revolving movement having a component parallel to the main axis of rotation "X" and a component perpendicular to the main axis of rotation "X". The said parallel component of the revolving movement causes a displacement of the engaging member 22 along the main axis of rotation "X" and therefore between the respective active and inactive positions, since the projection 36 is engaged inside the peripheral seat 34 and therefore conveys with it the engaging member 22 with a translatory movement along the main axis of rotation "X".
The perpendicular component of the said revolving movement of the projection 36 does not produce any action on the engaging member 22, the projection 36 being free to move along the peripheral seat 34.
With regard to the second centrifugal pump 7,
In accordance with the diagram shown in
The first volumetric pump 6 is connected to a respective filling pipe "P1" which departs downstream of the first pump 6 and upstream of the first three-way valve "V1" by means of a second three-way valve "V2" and leads into the tank 2. The second three-way valve "V2" therefore establishes fluid communication selectively between the first pump 6 and the first three-way valve "V1" or, alternatively, the filling pipe "P1" of the first pump 6. The first pump 6 is also connected, upstream thereof, to a respective supply line "A1" which can be associated with a source "S" of liquid, preferably water. In the case where the pumping unit 1 is mounted on an agricultural spraying machine, the source "S" could be a tank, a ditch or a water basin. A third three-way valve "V3" is therefore provided upstream of the first pump 6 and selectively supplies to the first pump 6 the liquid from the tank 2 or alternatively the water drawn via the supply pipe "A1" of the first pump 6. As a result thereof, in operating conditions, the first pump 6 is able to ensure autonomously a supply of the liquid to the tank 2, drawing it via the respective supply pipe "A1" and conveying it to the tank 2 via the respective filling pipe "P1", even though this means that, during this step, it is not possible to deliver the liquid through the delivery openings 4.
The second pump 7 is connected on its intake side to a respective supply pipe "A2" which can be associated with the said source "S" of liquid. The second pump 7 is also connected, on the delivery side, to a respective filling pipe "P2" leading into the tank 2. The second pump 7 is also advantageously connected to a stirring pipe "G" emerging in a bottom portion of the tank 2 or, more generally, in a portion thereof occupied by the liquid, in order to produce swirling movements in the said liquid, favouring the mixing of any components added to the said liquid.
A fourth three-way valve "V4" is therefore provided downstream of the second pump 7 and selectively establishes fluid communication between the second pump 7 and the respective filling pipe "P2" or, alternatively, the stirring pipe "G".
In certain applications, for example in agricultural machines for spraying liquid fertilizers or weedkillers or more generally for spraying chemical products mixed with water, the first pump 6 delivers a first liquid to the delivery openings 4 which is different from a second liquid supplied to the tank 2 by the second pump 7. Generally, the second liquid supplied to the tank 2 is water. Solid tablets containing chemical components are added, for example, to the water inside the tank 2 and, following the abovementioned stirring movement, dissolve in the water. The first pump 6, therefore, conveys to the delivery openings 4 a respective first liquid which may have properties different from those of the second liquid. This first liquid, in the circumstances described above, is an aqueous solution or a suspension, in water, of one or more given chemical substances.
If other components are not added to the liquid contained inside the tank 2, the first liquid would be entirely identical to the second liquid.
The present invention achieves the proposed objects, overcoming the drawbacks of the prior art.
The presence of means for transmission of the movement between the two pumps in the form of an epicyclic gearing achieves a considerable reduction in the dimensions of the said transmission means. In fact, the epicyclic gearing does not require the presence of transmission shafts which are typical of reducers of the known type and allows alignment of the drive shafts of the two pumps coaxially with each other.
In such a situation it is therefore possible to embed at least partially the transmission means inside a volume of the volumetric pump, achieving a reduction in the overall dimensions of the assembly formed by the pumps and the transmission means. Therefore, unlike the reducers of the known type which must be constrained to a fixed structure owing to their considerable mass, the epicyclic gearing according to the invention may advantageously be connected to one of the two pumps, for example the volumetric pump.
In fact, the direct connection between the two pumps, via the said transmission means, has an extreme constructional simplicity, complex members not being envisaged for distributing the movement from the Cardan joint to the two pumps.
The present invention achieves moreover the important advantage of rendering the operation of the two pumps independent of each other, since the reversible engaging means allow deactivation of the centrifugal pump while keeping the volumetric pump in operation, for example in conditions where the tank is full.
Moreover, it is also possible to supply the tank with the volumetric pump alone, the usefulness of which is particularly obvious in the case of malfunctioning of the centrifugal pump.
This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.