WO2008098854A1

WO2008098854A1 - Pumping device particularly for fluids containing solid suspensions

Info

Publication number: WO2008098854A1
Application number: PCT/EP2008/051356
Authority: WO
Inventors: Germano Zambaldo
Original assignee: Z.G. Camini Inox S.R.L.
Priority date: 2007-02-15
Filing date: 2008-02-04
Publication date: 2008-08-21
Also published as: ITVR20070024A1

Abstract

A pumping device (1) particularly for fluids containing solid suspensions, comprising a duct (2) for conveying the fluid to be pumped which has elastically flexible walls, at least one pumping assembly (3) being interposed along the conveyance duct (2) and comprising a box-like body (4) which is arranged around the conveyance duct (2) and delimits, with the conveyance duct, an actuation chamber (5), the actuation chamber (5) having an inlet (6) which can be connected on command to means (7) for feeding an actuation fluid under pressure, in order to produce a radial compression of the conveyance duct (2), and an outlet (8) for the outflow of the actuation fluid from the actuation chamber (5).

Description

PUMPING DEVICE PARTICULARLY FOR FLUIDS CONTAINING SOLID SUSPENSIONS Technical Field

The present invention relates to a pumping device particularly but not necessarily suitable for pumping fluids in general and more particularly liquids containing solid suspensions, even in high percentages, which have rapid settling, such as sludges or the like. Background Art

As is known, several types of pumps are currently available which are capable of pumping extremely dense fluids which are difficult to handle, such as for example liquids containing solid suspensions.

Among pumps of this kind it is possible for example to mention gear- type pumps, lobe-type pumps, piston pumps, single-screw pumps, membrane pumps, peristaltic pumps and so forth. The pumping efficiency of such pumps generally decreases as the flow-rate decreases or as the load of impurities and suspensions increases with respect to the percentage of fluid.

Moreover, such pumps are often subject to malfunctions caused mainly by the phase separation that occurs in certain fluids which contain solid suspensions due to the mechanical forces applied to the fluid.

The settling of solid suspensions can in fact hinder the free movement of the moving parts of the pump and therefore damage their operation. Disclosure of the Invention

The aim of the present invention is to provide a valid solution to the drawbacks noted above by providing a pumping device, particularly for fluids containing solid suspensions, which allows to convey fluids which contain solid suspensions without having the separation between the solid phase and the liquid phase.

Within this aim, an object of the invention is to provide a pumping device which allows to validly pump fluids which contain a high percentage of solid suspensions and has high efficiency even at extremely low flow- rates.

Another object of the invention is to provide a pumping device particularly for fluids containing solid suspensions which can be used in different fields of application, including biomedical ones.

Another object of the invention is to provide a pumping device which, due to its particular constructive characteristics, is capable of offering the greatest assurances of reliability and safety in operation.

Still another object of the present invention is to provide a pumping device which has an extremely simple structure and can be manufactured by means of commonly commercially available elements and materials so as to be advantageous also from a merely economical standpoint.

This aim and these and other objects which will become better apparent hereinafter are achieved by a pumping device particularly for fluids containing solid suspensions, according to the invention, characterized in that it comprises a duct for conveying the fluid to be pumped which has elastically flexible walls, at least one pumping assembly being interposed along said conveyance duct and comprising a box-like body which is arranged around said conveyance duct and delimits, with said conveyance duct, an actuation chamber, which has an inlet which can be connected on command to means for feeding an actuation fluid under pressure, in order to produce a radial compression of said conveyance duct, and which has an outlet for the outflow of said actuation fluid from said actuation chamber. Brief Description of the Drawings

Further characteristics and advantages of the invention will become better apparent from the description of some preferred but not exclusive embodiments of the pumping device according to the invention, illustrated by way of non-limiting example in the accompanying drawings, wherein: Figure 1 is a perspective view of the device according to the invention;

Figure 2 is a cutout perspective view of the device according to the invention;

Figure 3 is an enlarged-scale longitudinal sectional perspective view of a detail;

Figure 4 is a partially sectional plan view of the device according to the invention;

Figure 5 is a schematic perspective view of another embodiment of the device according to the invention; Figure 6 is a partial sectional perspective view of the embodiment of

Figure 5;

Figures 7 to 10 are schematic longitudinal sectional views of the different steps of the operation of the device according to the invention;

Figure 11 is a view of a detail of a possible constructive variation of the device according to the invention, shown in longitudinal cross-section;

Figure 12 is a longitudinal sectional and enlarged-scale view of a detail of the embodiment of Figures 5 and 6. Ways of carrying out the Invention

With reference to the figures, the pumping device, particularly for fluids containing solid suspensions, according to the invention, generally designated by the reference numeral 1 , comprises a duct 2 for conveying the fluid to be pumped which has elastically flexible walls and is constituted for example by a tube made of an elastomer of any type.

Along the conveyance duct 2 there is at least one interposed pumping assembly 3, and more preferably there are at least two separate pumping assemblies 3, which are arranged in mutual succession along the extension of the conveyance duct 2.

It should be noted that the number of pumping assemblies 3 can be changed as a function of the different pumping requirements and of the type of fluid to be pumped. Each pumping assembly 3 is provided with a box-like body 4 which is arranged around the conveyance duct 2 and is radially inextensible with respect to the conveyance duct 2.

For this purpose, the box-like body 4 is preferably made of metallic material, such as for example steel, or made of fabric-reinforced or wire- reinforced rubber.

More particularly, the box-like body 4 of each pumping assembly 3 delimits, together with the conveyance duct 2, a corresponding actuation chamber 5. The actuation chamber 5 of each pumping assembly 3 is provided with an inlet 6, which is provided in the respective box-like body 4 and can be connected on command to means 7 for feeding a pressurized actuation fluid, which allow to introduce said actuation fluid in the actuation chamber 5 in order to produce a radial compression of the conveyance duct 2 which allows to impart to the fluid to be pumped a motion inside the conveyance duct 2.

It should be noted that the actuation fluid used can be a gas and more particularly can be compressed air or a liquid such as oil or water.

An outlet 8 for the outflow of the actuation fluid from the respective actuation chamber 5 is further provided in the box-like body 4 of each pumping assembly 3.

Conveniently, the outlet 8 of the actuation chamber 5 of each pumping assembly 3 can be connected on command to drawing means 9 for drawing the actuation fluid, which are designed to aspirate the actuation fluid from the actuation chamber 5 so as to produce a radial expansion of the conveyance duct 2 which allows to draw the fluid to be pumped into the portion of the conveyance duct 2 that is affected by the corresponding pumping assembly 3.

As shown, the box-like body 4 of each pumping assembly 3 is conveniently provided by a tubular element 10, which is arranged coaxially with respect to the conveyance duct 2.

With this structure, the actuation chamber 5 of each pumping assembly 3 in practice is defined by an annular interspace which is comprised between the internal surface of the corresponding tubular element 10 and the outer surface of the conveyance duct 2.

Preferably, the inlet 6 and the outlet 8 of the actuation chamber 5 of each pumping assembly 3 are constituted by respective openings provided in the tubular element 10 and arranged on diametrically mutually opposite sides with respect to the axis of the tubular element 10. Advantageously, intake valve means 11 are associated with the inlet 6 of the actuation chamber 5 of each pumping assembly 3 and are constituted preferably by an electric valve and are designed to control the injection of the actuation fluid into the corresponding actuation chamber 5.

Likewise, the outlet 8 of the actuation chamber 5 of each pumping assembly 3 is conveniently controlled by outlet valve means 12, which are also advantageously constituted by an electric valve and are designed to connect the corresponding actuation chamber 5 to the drawing means 9 in order to produce the outflow of the actuation fluid from the actuation chamber 5. Conveniently, the means 7 for feeding the actuation fluid are provided by a delivery line 13 which extends from an assembly 13a for dispensing the actuation fluid under pressure, of any known type, and which, by means of the interposition of the various intake valve means 1 1, is connected to the actuation chamber 5 of each one of the pumping assemblies 3.

The means 9 for drawing the actuation fluid instead comprise a suction line 14, which is connected to a suction assembly 14a for the actuation fluid, of any suitable type, and which, by means of the corresponding outlet valve means 12, is connected to the actuation chambers 5 of the various pumping assemblies 3. According to a possible constructive variation shown in Figure 11 , the inlet 6 and the outlet 8 of the actuation chamber 5 of each pumping assembly 3 can also be both defined by a single opening 4a, provided in the box-like body 4 of the respective pumping assembly 3. In this case, the opening 4a of each pumping assembly 3 is conveniently connected to the delivery line 13 and to the suction line 14 by means of a respective three- way valve 4b.

It should be noted that the delivery line 13 and the suction line 14 can form an open circuit, as in the case in which the dispensing assembly 13a and the suction assembly 14a of the actuation fluid are provided respectively by a compressed air generator and by a vacuum pump which are separated one another, or can form a closed circuit, as in the case in which the dispensing assembly 13a and the suction assembly 14a of the actuation fluid are obtained by a means of a hydraulic controller in which both are integrated.

Advantageously, the intake valve means 1 1 and the outlet valve means 12 are functionally connected to a programmable control unit 100, which can be of the electromechanical type or more preferably of the electronic type, such as for example a PLC control system. In practice, by means of the control unit 100 it is possible to perform an automatic actuation of the pumping device according to the invention in manners which can be differentiated by the user in relation to the specific requirements of use.

With particular reference to Figure 3, it can be seen that the tubular element 10 of each pumping assembly 3 can be conveniently connected hermetically to the tubular element 10 of the contiguous pumping assembly.

Moreover, hermetic separation means 20 are interposed advantageously between the actuation chambers 5 of the various contiguous pumping assemblies 3 and allow to achieve a hermetic seal between each actuation chamber 5, consequently making each individual pumping assembly 3 of the device according to the invention independent.

With a structure of this type, in practice it is possible to assemble the device according to the invention by using the various pumping assemblies as components of a modular system, allowing the device according to the invention to have the broadest range of possible uses.

In greater detail, the tubular element 10 of each pumping assembly 3 has, at one of its ends, a male connecting portion 15, which can be mated with the tubular element 10 of a contiguous pumping assembly, and has, at its opposite end, a female connecting portion 16 in which it is possible to insert coaxially the male connecting portion 15 provided on the tubular element 10 of another contiguous pumping assembly.

As shown, the male connecting portion 15 is provided for example by a first axial extension 17a of the tubular element 10 provided with a smaller outside diameter than the remaining part of the tubular element, while the female connecting portion 16 is obtained by providing a second axial extension 17b of the tubular element 10 whose inside diameter is larger than the remaining part of the tubular element 10 and substantially equal to the outside diameter of the first axial extension 17a.

It should be noted that the connection between the male connecting portion 15 and the female connecting portion 16 can be provided through engagement by pressing, as in the example shown in the figures, or by means of a threaded coupling provided by a male thread defined on the male connecting portion 15 and engageable with a female complementary thread provided on the female connecting portion 16. As an alternative, the interconnection among the several tubular elements 10 can be provided by an interlocking coupling of the male and female type with a retention element, such as for example a locking grub, or by means of an appropriately provided interposed connecting union.

Advantageously, the hermetic separation means 20 which act between the actuation chambers 5 of each pair of contiguous pumping assemblies comprise respectively a sealing ring 21, which is arranged inside the conveyance duct 2, substantially at the region of mutual mating between the tubular elements 10 that belong to the corresponding pair of contiguous pumping assemblies. In particular, each sealing ring 21 is structured so as to press a portion of wall of the conveyance duct 2 against the internal surface of the corresponding tubular elements 10 which are coupled.

It should be noted that the sealing rings 21 can be made of different materials, such as for example metal, plastics or ceramic, depending on the intended application of the device according to the invention.

Preferably, the hermetic separation means 20 further comprise a respective annular seat 22 in which the portion of wall of the conveyance duct 2 engaged by the corresponding sealing ring 21 is accommodated.

As can be seen, the annular seat 22 is advantageously defined partly by one and partly by the other of the mutually coupled tubular elements 10 which belong to a respective pair of contiguous pumping assemblies 3.

Conveniently, the tubular element 10 of each pumping assembly 3 can have, proximate to the opposite ends, two respective circumferential protrusions 23 which extend in the direction of its axis and delimit laterally, with a corresponding circumferential protrusion 23 supported by the tubular element 10 of a contiguous pumping assembly, a respective annular seat 22.

Moreover, the circumferential protrusions 23 engage the wall of the conveyance duct 2, forming with several sealing rings 21 a guide for the wall of the conveyance duct 2 which allows to increase the fluid seal among the several actuation chambers 5 of the several pumping assemblies 3.

Moreover, the device according to the invention is conveniently completed by fastening means which allow to keep the tubular elements 10 of the several pumping assemblies 3 coupled and fastened to each other.

Such fastening means are preferably provided by way of a pair of flanged elements 30, which are arranged at the opposite ends of the plurality of pumping assemblies 3 arranged mutually side-by-side along the conveyance duct 2.

The flanged elements 30 are mutually joined by interconnecting tension elements 31, each of which is constituted by a threaded rod 32 which is engaged by a respective pair of nuts 33 which can be fastened against the faces of the flanged elements 30 oriented in the opposite direction with respect to the pumping assemblies 3.

In a possible constructive variation of the device according to the invention shown in Figures 5 and 6, the box-like body 4 of each pumping assembly 3 is constituted by an annular element 40, which is preferably made of silicone rubber and is arranged coaxially to the axis of the conveyance duct 2 and is shaped so as to define a circumferential hollow 41 which is open toward the corresponding axis in order to provide, in cooperation with the conveyance duct 2, a corresponding actuation chamber 5.

In this case, the hermetic separation means 20 are conveniently obtained by means of circular fins 42, which protrude radially from the outer surface of the conveyance duct 2 and are formed monolithically with the conveyance duct 2, and between which the annular elements 40 of the several pumping assemblies 3 are positioned.

Advantageously, the circular fins 42 have, in a radial cross-section, substantially a T-shaped configuration and more specifically, along the outer circumferential perimeter of each circular fin 42 axial locking borders 43 are provided which define, on mutually opposite sides with respect to the plane of arrangement of the corresponding circular fin 42, two annular engagement seats 44, which are designed to accommodate respective peripheral coupling edges 45 defined on the annular elements 40.

Preferably, a port 46 is provided within each annular element 40 and provides the inlet 6 and the outlet 8 of the corresponding actuation chamber 5. The port 46 of each annular element is connected to an actuation tube 47, through which the actuation fluid is introduced in or extracted from the corresponding actuation chamber 5.

Advantageously, the actuation tubes 47 of the several annular elements 40 are functionally connected to a controller 48, which accommodates the feed means 7 and the drawing means 9 for the actuation fluid. More particularly, for each actuation tube 47 there is a corresponding control valve 49 which is connected to the feed means 7 and to the drawing means 9 of the actuation fluid. It is further possible to integrate in the controller 48 the control unit 100, which in this case is functionally connected to the control valves 49 of the several actuation tubes 47 and is advantageously programmable by the user by means of appropriately provided interfacing devices 50, of any known type, which are provided on the controller 48 in order to set the operating parameters of the device according to the invention. Conveniently, moreover, the annular elements 40 of the several pumping assemblies 3 and at least one portion of the actuation tubes 47 are enclosed within an outer cylindrical enclosure 51 , which is preferably rigid with respect to a radial compression or expansion and for this purpose is advantageously made of wire-reinforced rubber or other plastic synthetic material with a reinforcement mesh embedded inside it.

Conveniently, the outer cylindrical enclosure 51 has, in its side wall, an open region 51a for the exit of the actuation tubes 47 and is further closed, at its opposite ends, by two plugs 52 which have an axial passage which is crossed by the conveyance duct 2. As shown, the plugs 52 can be arranged for example in the opposite direction with respect to the outer cylindrical enclosure 51, with a conical shape which converges toward the conveyance duct 2.

Conveniently, the space comprised between the outer cylindrical enclosure 51 and the several pumping assemblies 3 can be filled at least partially by injecting a filler material, such as for example silicone rubber or other suitable material.

As pointed out in Figure 5, it should be noted that at the actuation chambers 5 of the several pumping assemblies 3 the conveyance duct 2 can conveniently have a reduction 53 in its wall thickness in order to increase its flexibility.

This refinement of course can be adopted also in other embodiments. It should be noted that with the structure of the device according to the invention in the embodiment of Figures 5 and 6 a considerable simplification of the assembly of the device according to the invention and an improvement of its performance are achieved, in addition to the advantage of being able to avoid the use of the sealing rings 21.

Finally, for the sake of completeness, it should be noted that in any embodiment, in order to facilitate maintenance operations in the specific fields of use, it is optionally possible to provide, inside the conveyance duct 2, a detachable service tube (not shown), also provided with elastically flexible walls, which is designed to convey the fluid to be pumped and is therefore designed to come directly into contact with the fluid to be pumped, while the conveyance duct 2 in this case has the function of an actuation element of the service tube. Operation of the device according to the invention is as follows.

With reference to Figures 7 to 10, one proceeds initially by opening the intake valve means 1 1 of the several pumping assemblies 3 and by closing their outlet valve means 12 so as to introduce pressurized actuation fluid into their actuation chambers 5 and accordingly produce the compression of the portion of the conveyance duct 2 that is affected by the several pumping assemblies 3 until complete collapse of its walls is achieved.

Starting from this condition, the first pumping assembly 3 in the series arrangement of the several pumping assemblies 3 along the conveyance duct 2 is actuated, along the direction of motion that one wishes to impart to the fluid to be pumped, opening its outlet valve means 12 and instead closing its intake valve means 1 1 , so as to achieve the outflow of the actuation fluid from its actuation chamber 5 and thus determine the radial expansion of the portion of the conveyance duct 2 that is affected by the first pumping assembly 3.

By doing so, the fluid to be pumped is pushed from a region arranged upstream of the first pumping assembly 3 toward the first pumping assembly 3.

At this point, the second pumping assembly 3 arranged, along the direction of motion that one wishes to impart to the fluid to be pumped, directly downstream of the first pumping assembly in the series arrangement of the various pumping assemblies 3 along the conveyance duct 2 is actuated, and more precisely its outlet valve means 12 are opened and its intake valve means 1 1 are closed so as to produce the radial expansion of the portion of the conveyance duct 2 that is affected thereby.

At the same time, the outlet valve means 12 of the first pumping assembly 3 are closed and its intake valve means 11 are opened, so as to produce the radial compression of the corresponding portion of the conveyance duct 2. In this manner, the movement of the fluid to be pumped along the conveyance duct 2 from the first pumping assembly toward the second pumping assembly 3 is achieved.

The pumping cycle then continues by progressively actuating sequentially the subsequent pumping assemblies 3, in a manner similar to what has been described above.

It should be noted that operation of the device according to the invention can also be modified with respect to the manner described above, in order to adapt it to the different types of fluids to be pumped, by performing a different programming of the control unit 100 that controls the intake valve means 11 and the outlet valve means 12 of the several pumping assemblies 3.

Thus, for example, it is possible to perform programs to convey the fluid to be pumped along the conveyance duct in one direction and then in the opposite direction, working in practice first by delivery and then by suction, so as to achieve an alternating motion of the fluid to be pumped into the conveyance duct 2.

Another possible operating mode which can be set by programming the control unit 100 is the one that consists in actuating at least two pumping assemblies which are spaced one another along the conveyance duct 2 so as to compress the portions of the conveyance duct 2 that correspond to them, until their walls come into mutual contact, thus closing the conveyance duct 2 in two points, and in then actuating sequentially the several pumping assemblies 3 located between these two points of the conveyance duct 2 in order to impart to the fluid to be pumped an alternating movement in one direction and in the other direction, so as to avoid settling of the suspensions contained therein.

Moreover, by varying the level of pressure in the delivery line 13 and in the suction line 14, it is possible to vary the outflow rate of the fluid to be pumped along the conveyance duct 2. Moreover, it should be added that especially if the fluid to be pumped is not very viscous and contains a limited amount of suspensions, the device according to the invention can operate correctly even without requiring the forced suction of the actuation fluid from the actuation chambers 5 by way of the drawing means 9, since after interrupting the introduction of the pressurized actuation fluid into the actuation chambers, the conveyance duct 2, by way of the elastic return of the material used to provide it, can automatically return to its original shape.

In practice it has been found that the invention fully achieves, in all of its embodiments, the intended aim and objects. In particular, the fact is stressed that the device according to the invention, thanks to its possibility of modular assembly, can be adapted easily to the different operating requirements.

Another advantage of the invention resides in the complete programmability of the pumping sequence, allowing in a very simple manner the provision of multiple programs designed specifically for the type of fluid being conveyed or for a particular type of use.

All the characteristics of the invention indicated above as advantageous, convenient or the like may also be omitted or be replaced with equivalents. The individual characteristics presented with reference to general teachings or particular embodiments may all be present in other embodiments or may replace characteristics in these embodiments.

The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims.

In practice, the materials used, so long as they are compatible with the specific use, as well as the shapes and dimensions, may be any according to requirements.

All the details may further be replaced with other technically equivalent elements.

The disclosures in Italian Patent Application no. VR2007A000024, from which this application claims priority, are incorporated herein by reference.

Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

1. A pumping device particularly for fluids containing solid suspensions, characterized in that it comprises a duct for conveying the fluid to be pumped which has elastically flexible walls, at least one pumping assembly being interposed along said conveyance duct and comprising a box-like body which is arranged around said conveyance duct and delimits, with said conveyance duct, an actuation chamber, which has an inlet which can be connected on command to means for feeding an actuation fluid under pressure, in order to produce a radial compression of said conveyance duct, and which has an outlet for the outflow of said actuation fluid from said actuation chamber.

2. The pumping device according to claim 1, characterized in that it comprises at least two pumping assemblies arranged in mutual succession along the extension of said conveyance duct, said pumping assemblies each having a respective box-like body which is arranged around said conveyance duct and delimits, with said conveyance duct, a corresponding actuation chamber, which can be connected on command, by means of one of its inlets, to means for feeding a pressurized actuation fluid, in order to produce the radial compression of said conveyance duct, and having its own outlet for the outflow of said actuation fluid.

3. The pumping device according to claim 1 or 2, characterized in that said outlet can be connected on command to means for drawing said actuation fluid from said actuation chamber, in order to produce a radial expansion of said conveyance duct.

4. The pumping device according to one or more of the preceding claims, characterized in that said box-like body comprises a tubular element which is arranged coaxially with respect, to said conveyance duct, said actuation chamber being defined by an annular interspace which is arranged between the internal surface of said tubular element and the outer surface of said conveyance duct.

5. The pumping device according to one or more of the preceding claims, characterized in that said inlet and said outlet are provided by respective openings which are defined in said tubular element on diametrically mutually opposite sides with respect to the axis of said tubular element.

6. The pumping device according to one or more of the preceding claims, characterized in that it comprises, for each of said pumping assemblies, intake valve means for said actuation fluid which are adapted to control the inlet of the corresponding actuation chamber, outlet valve means for said actuation fluid being provided for each of said pumping assemblies, said means being adapted to control the outlet of the corresponding actuation chamber.

7. The pumping device according to one or more of the preceding claims, characterized in that said feed means comprise a line for the delivery of said pressurized fluid which is connected to the actuation chamber of each one of said pumping assemblies by way of the interposition of the respective intake valve means, said drawing means comprising a suction line for said actuation fluid which is connected to the actuation chamber of each one of said pumping assemblies by way of the interposition of the corresponding outlet valve means.

8. The pumping device according to one or more of the preceding claims, characterized in that said intake valve means and said outlet valve means can be driven functionally by a programmable control unit.

9. The pumping device according to one or more of the preceding claims, characterized in that the tubular element of each one of said pumping assemblies can be connected hermetically to the tubular element of the contiguous pumping assembly.

10. The pumping device according to one or more of the preceding claims, characterized in that it comprises hermetic separation means which are interposed between the actuation chambers of mutually contiguous pumping assemblies.

1 1. The pumping device according to one or more of the preceding claims, characterized in that the tubular element of each pumping assembly has, at one end, a male connecting portion which can be inserted axially in the tubular element of a contiguous pumping assembly and, at its opposite end, a female connecting portion which is adapted to accommodate coaxially the male connecting portion of the tubular element of another contiguous pumping assembly.

12. The pumping device according to one or more of the preceding claims, characterized in that said male connecting portion comprises a first axial extension of said tubular element which has a reduced outside diameter with respect to the remaining part of said tubular element, said female connecting portion comprising a second axial extension of said tubular element which has a larger inside diameter than the remaining part of said tubular element.

13. The pumping device according to one or more of the preceding claims, characterized in that said hermetic separation means comprise, in the region for mutual coupling of the tubular elements of each pair of contiguous pumping assemblies, a sealing ring which is arranged inside said conveyance duct and is adapted to press a portion of a wall of said conveyance duct against the internal surface of the mutually coupled tubular elements.

14. The pumping device according to one or more of the preceding claims, characterized in that said hermetic separation means comprise an annular seat for said portion of wall of said conveyance duct, said annular seat being defined partly in one and partly in the other one of the mutually coupled tubular elements.

15. The pumping device according to one or more of the preceding claims, characterized in that said annular seat is defined between a pair of circumferential protrusions which are defined by the tubular elements in their mutual coupling region and lie in the direction of the axis of the tubular elements.

16. The pumping device according to one or more of the preceding claims, characterized in that it comprises means for fastening one another the tubular elements of the contiguous pumping assemblies.

17. The pumping device according to one or more of the preceding claims, characterized in that said fastening means comprise a pair of flanged end elements which are mutually connected by interconnection tension elements.

18. The pumping device according to one or more of the preceding claims, characterized in that said box-like body comprises an annular element which defines a hollow which is open toward its own axis in order to provide, in cooperation with said conveyance duct, a corresponding actuation chamber.

19. The pumping device according to one or more of the preceding claims, characterized in that said annular element is made of silicone rubber.

20. The pumping device according to one or more of the preceding claims, characterized in that said hermetic separation means comprise a respective circular fin, which protrudes radially from the outer surface of said conveyance duct and is interposed between the annular elements of two contiguous pumping assemblies, said circular fin being provided monolithically with said conveyance duct.

21. The pumping device according to one or more of the preceding claims, characterized in that said circular fin is provided perimetrically with axial locking borders which define, on mutually opposite sides with respect to the plane of arrangement of said circular fin, two engagement seats for respective peripheral coupling edges which are defined on the annular elements of two contiguous pumping assemblies.

22. The pumping device according to one or more of the preceding claims, characterized in that said circular fin has, in a radial cross-section, a substantially T-shaped configuration.

23. The pumping device according to one or more of the preceding claims, characterized in that it comprises an outer cylindrical enclosure which is arranged substantially coaxially to said conveyance duct in order to accommodate said pumping assemblies.

24. The pumping device according to one or more of the preceding claims, characterized in that said outer cylindrical enclosure is made of wire-reinforced rubber.

25. The pumping device according to one or more of the preceding claims, characterized in that the space comprised between said outer cylindrical enclosure and said pumping assemblies is at least partially filled by means of a filler material.

26. The pumping device according to one or more of the preceding claims, characterized in that said conveyance duct has a reduction in its wall thickness at the actuation chambers of said pumping assemblies.