WO2019166954A1

WO2019166954A1 - Vibration pump

Info

Publication number: WO2019166954A1
Application number: PCT/IB2019/051555
Authority: WO
Inventors: Giuseppe Marone; Alessandro Rovera; Paolo Da Pont; Paolo Ravedati; Marco BUZZI; Marco GAUDINO; Piero AMICO
Original assignee: Elbi International S.P.A.
Priority date: 2018-02-27
Filing date: 2019-02-27
Publication date: 2019-09-06
Also published as: IT201800003064A1; EP3759347A1

Abstract

The pump comprises: a piston (2) at least partially made of ferromagnetic material; and a hollow body (6) configured for being crossed by a flow of fluid and comprising a work chamber (7) in which the piston (2) can reciprocate in a guided manner. The piston (2) defines in the work chamber (7) an inlet chamber (36) and a compensation chamber (38) intended for being crossed by the fluid. The inner surface of the work chamber (7) has at least one recess (42) defining at least one communication duct that fluidically connects the inlet chamber (36) and the compensation chamber (38). There is also a solenoid (4) arranged around the hollow body (6) and configured for actuating the piston (2) electromagnetically. Two ferromagnetic elements (5, 5') are arranged around the hollow body (6) and positioned transversally between the solenoid (4) and the hollow body (6). The ferromagnetic elements (5, 5') are laterally spaced apart and define at least one perimetrical interruption (G, G') in between. The recess (42) is located in a respective perimetrical interruption (G, G') and is laterally delimited by the perimetrical interruption (G, G').

Description

VIBRATION PUMP

DESCRIPTION

Technical field

The present invention relates to a vibration pump for pumping a fluid, which can be used, for example, in machines for making coffee, tea or other beverages. Besides, the pump can also be used in other apparatus, such as household appliances .

Background art

The vibration pumps known in the art comprise a work chamber in which the core is adapted to slide in a reciprocating manner. During such motion, the core divides the work chamber into two sub-chambers adapted to be filled with fluid: on one side of the core there is a pumping chamber, whereas on the other side there is a compensation chamber. Such two chambers are fluidically connected, so as to minimize the sliding resistance of the piston in the fluid. Generally, there are ferromagnetic elements, in particular metallic ones, interposed between the coil and the core, in a position radially external to the cylinder, which are useful to increase the magnetic effect of the coil on the core. The ferromagnetic elements usually have an annular shape, e.g. a circular or "C" shape.

According to patent application EP 0288216 Al, recesses are formed on the inner surfaces of the cylinder, which define the communication duct (Fig. 5) . The core slides on protrusions (designated by numeral 25), between which the recesses are located.

However, this type of system suffers from a number of drawbacks. One drawback is due to the long distance between the core and the ferromagnetic elements because of the presence of the protrusions, resulting in a reduced magnetic effect of the coil on the core. Moreover, the pump is bulky because of such distance.

Summary of the invention

It is one object of the present invention to provide a vibration pump which can overcome this and other drawbacks of the prior art, while at the same time being simple and economical to manufacture.

According to the present invention, this and other objects are achieved through a vibration pump made in accordance with the appended independent claim.

It is to be understood that the appended claims are an integral part of the technical teachings provided in the following detailed description of the present invention. In particular, the appended dependent claims define some preferred embodiments of the present invention, which include some optional technical features.

Brief description of the drawings

Further features and advantages of the present invention will become apparent from the following detailed description, which is supplied merely by way of non-limiting example with reference to the annexed drawings, wherein:

- Figure 1 is a longitudinal sectional view of a pump in accordance with an exemplary embodiment of the present invention;

- Figure 2 is a perspective view of a pump according to an exemplary embodiment of the present invention;

- Figure 3 is a perspective view of the pump of Figure 2, with the cover removed;

- Figure 4 is a perspective view of the cover with the impeller of a pump according to an exemplary embodiment of the present invention; - Figure 5 is another longitudinal sectional view of a pump in accordance with an exemplary embodiment of the present invention;

- Figure 6 is a partial perspective view of a pump according to an embodiment of the invention, showing the inside of the cylinder;

- Figure 7 is a cross-sectional view of the cylinder, showing some details of a pump made in accordance with an exemplary embodiment of the present invention;

- Figure 8 is a partial perspective view of a pump made in accordance with an exemplary embodiment of the present invention;

- Figure 9 is a view similar to Figure 8, showing also ferromagnetic elements arranged around the hollow body;

- Figures 10 and 11 are longitudinal sectional and perspective views, respectively, of a reel of a solenoid applicable to a pump made in accordance with an exemplary embodiment of the present invention;

- Figure 12 is a longitudinal sectional view of a pump made in accordance with a further embodiment of the present invention, such view being similar to the view shown in Figure 5; and

- Figure 13 is a partial perspective view of the pump of Figure 12, such view being similar to the view shown in Figure 6.

Detailed description of the invention

With particular reference to Figure 1, the present invention concerns a vibration pump (hereafter also referred to simply as "pump") substantially extending along a longitudinal axis x-x. Therefore, the terms "axial", "longitudinal", "transversal" and "radial" as used in the following description should be considered to refer to said longitudinal axis x-x.

The pump comprises a piston or core 2 made at least partially of ferromagnetic material, and a hollow body or cylinder 6 configured for being crossed by a flow of fluid.

The hollow body or cylinder 6 comprises a work chamber 7, in which core 2 is adapted to reciprocate in a guided manner .

Piston or core 2 defines in work chamber 7 an inlet chamber 36 and a compensation chamber 38 intended for being crossed by the fluid.

The inner surface of work chamber 7 has at least one recess (in particular, receding transversally or radially) defining a communication duct that fluidically connects inlet chamber 36 and compensation chamber 38. Preferably, as shown in the drawings, the inner surface of the work chamber comprises a pair of such recesses, both designated by reference numeral 42.

In the illustrated embodiment, each recess 42 extends in a substantially longitudinal or axial direction to form said communication duct.

The pump further comprises a solenoid 4 arranged around the hollow body or cylinder 6 and configured for actuating piston or core 2 electromagnetically .

Furthermore, the pump comprises at least one pair of ferromagnetic elements 5, 5' arranged around cylinder 6 and positioned transversally between solenoid 4 and core 2.

With particular reference to Figures 7, 10 and 11, ferromagnetic elements 5, 5' are laterally spaced apart and define at least one perimetrical interruption in between. Preferably, as can be seen in said figures, ferromagnetic elements 5, 5' define, between themselves, a pair of such perimetrical interruptions, designated by references G, G'. Due to the above-mentioned features, the transversal distance between ferromagnetic elements 5, 5' and core 2 is considerably reduced. In other words, between core 2 and ferromagnetic elements 5, 5' - which contribute to effectively conducting the magnetic flux generated by solenoid 4 towards core 2 - only cylinder 6 is transversally interposed, without any other interstices or gaps that would cause a substantial dispersion of the magnetic flux.

Cylinder 6 and the at least one ferromagnetic element 5, 5' are configured in a manner such that the at least one recess 42 defining the communication duct is absent between the at least one ferromagnetic element 5, 5' and core 2. Therefore, with reference to a transversal or radial direction (e.g. relative to a longitudinal axis x-x of cylinder 6), between the at least one ferromagnetic element 5, 5' and core 2 there is no recess 42. In particular, cylinder 6 extends along a longitudinal axis x-x. With reference to a radial direction relative to longitudinal axis x-x (Fig. 7), between ferromagnetic element 5, 5' and core 2 there is only a lateral surface of cylinder 6. Conversely, in areas comprising recess 42 that defines the communication duct, ferromagnetic element 5, 5' is absent, which is located in a radially external position relative to recess 42. Advantageously, as mentioned above, the radial distance between ferromagnetic element 5, 5' and core 2 is minimal because there is no recess 42 in between, resulting in a maximized magnetic effect on core 2. In fact, the distance between the outer surface of core 2 and the inner surface of ferromagnetic element 5, 5' substantially corresponds to the thickness of the walls of cylinder 6. This makes it possible to produce a solenoid 4 and/or an electric circuit that generate a weaker magnetic field, the effect on core 2 being equal; for example, it is possible to reduce the quantity of copper in solenoid 4. In addition, such a configuration allows reducing the transversal dimension of the pump.

The recess is located on an inner surface of cylinder 6 in work chamber 7.

In the illustrated embodiment, the pump also comprises:

- an inlet duct 8 and an outlet duct 10, allowing a fluid to flow in cylinder 6,

- valve means for generating the flow of fluid from inlet duct 8 to outlet duct 10 when core 2 reciprocates in cylinder

6.

Preferably, ferromagnetic elements 5, 5' are transversally in contact with the outer surface of hollow body 6, so that recess 42 does not extend transversally between hollow body 6 and ferromagnetic elements 5, 5'.

Preferably, according to the embodiment shown in Figure 7, with reference to a cross-section of cylinder 6, recess 42 defines a respective protrusion 48 on an outer surface of cylinder 6, and the pair of ferromagnetic elements 5, 5' end at protrusion 48. Moreover, just like associated recess 42, corresponding protrusion 48 extends in a substantially axial or longitudinal direction. Solenoid 4 is in a position radially external to core 2. Advantageously, at least one ferromagnetic element 5, 5', conveniently made of metal, is interposed between solenoid 4 and core 2. A plurality of ferromagnetic elements 5, 5' may be used. In the example there are four ferromagnetic elements 5, 5', which preferably have a "C" shape or a semicircular shape. The at least one ferromagnetic element 5, 5' is arranged in a radially external position relative to core 2 and cylinder 6. In particular, the at least one ferromagnetic element 5, 5' is arranged circumferentially around core 2. Ferromagnetic element 5, 5' may be a permanent magnet. Core 2 is conveniently made of metallic material. Solenoid 4 is conveniently housed in a respective reel or housing 40 mounted to cylinder 6. Ferromagnetic elements 5, 5' are longitudinally arranged inside work chamber 7, with reference to axis x-x of cylinder 6.

One advantage of the plurality of ferromagnetic elements 5, 5' is the simplicity of assembling the same, particularly when there are pairs of semicircular ferromagnetic elements 5, 5', as in the illustrated example.

In particular, there are preferably two groups of ferromagnetic elements, wherein a first group comprises a pair of first ferromagnetic elements 5 and a pair of second ferromagnetic elements 5'. The first ferromagnetic elements 5 and the second ferromagnetic elements 5' are axially spaced apart. In addition, the second ferromagnetic elements 5' are laterally spaced apart and define at least one respective perimetrical interruption in between, in which recess 42 is situated and laterally delimited, being in particular defined by the first ferromagnetic elements 5. In particular, the second ferromagnetic elements 5' define a pair of perimetrical interruptions G' in which respective transversal recesses 42 are defined and delimited between the first ferromagnetic elements.

Both groups or pairs of ferromagnetic elements 5, 5' are situated in a circumferential position around cylinder 6. Such groups are aligned along axis x-x. In general, the at least one ferromagnetic element 5, 5' may be shaped like an arc of circumference. Preferably, the pump comprises a plurality of groups of ferromagnetic elements 5 (or 5'), wherein each group comprises more than one pair of ferromagnetic elements 5 (or 5'), wherein cylinder 6 and ferromagnetic elements 5 (or 5') are configured in a manner such that the at least one recess 42 defining the communication duct is absent between them. Ferromagnetic elements 5 (or 5') belonging to one group are arranged at substantially the same height, with reference to the longitudinal direction, along axis x-x of cylinder 6. Fig. 7 shows the cross-section of one of the two groups of the variant shown in Fig. 1. Conveniently, all ferromagnetic elements 5, 5' of the pump are equal, and in particular have the same shape.

As can be seen in the drawings, the peripheral development of the at least one ferromagnetic element 5, 5' around cylinder 6 is delimited by the at least one protrusion 48. In the example there are two protrusions 48, between which the pairs of ferromagnetic elements 5, 5' are arranged. In particular, protrusion 48 is parallel to axis x-x of cylinder 6. In fact, protrusion 48 conveniently follows the development of respective recess 42. In particular, in a cross-sectional view, the two ends of ferromagnetic elements 5 rest on protrusions 48.

As aforementioned, according to a preferred embodiment of the present invention, the illustrated pump comprises a plurality of (e.g. two) recesses 42 corresponding to a plurality of respective protrusions 48, and a plurality (e.g. two groups or pairs) of ferromagnetic elements 5, 5'. Therefore, communication ducts 42 alternate with ferromagnetic elements 5, 5'. In particular, the ferromagnetic elements 5, 5' are shaped like an arc of circumference. Preferably, recesses 42 are angularly equidistant from axis x-x of cylinder 6.

Recess 42 is configured in such a way that compensation chamber 38 communicates with recess 42 through an aperture having an axis substantially parallel to axis x-x, through which the fluid can flow in a prevalently axial direction, with reference to said axis x-x. As it flows through the aperture between recess 42 and compensation chamber 38, the fluid follows a trajectory that is substantially parallel to axis x-x. Therefore, the fluid flows towards compensation chamber 38 with little or no diversion, and therefore with low load losses. Moreover, as will become apparent from the present description, it is possible to create a core 2 that is simpler and more economical to manufacture. The communication duct defined by recess 42 has two apertures facing into pumping chamber 36 and into compensation chamber 38. In the preferred variant illustrated herein, also pumping chamber 36 communicates with recess 42 through an aperture having an axis that is substantially parallel to axis x-x, and through which the fluid can flow in a prevalently axial direction, with reference to said axis x-x. As already specified, the pump may comprise a plurality of recesses 42.

In particular, the fluid is intended to flow between said two apertures in the axial direction, i.e. prevalently parallel to axis x-x. Preferably, the communication duct defined by recess 42 is straight, in particular substantially parallel to axis x-x.

In particular, the pump has at least one elastic means, such as a spring 11, for bringing core 2 into an idle position when said core 2 is not subject to the magnetic action of solenoid 4. As is known, solenoid 4 is adapted to generate a time-variable magnetic field in order to move core 2, which, by co-operating with the at least one elastic means, will move in a reciprocating manner, covering a stroke within cylinder 6. Preferably, one end of spring 11 is constrained to core 2 (e.g. by welding or other mechanical constraints) in both directions of sliding of said core 2, and therefore it 11 can work both under traction and under compression. Hence, in the illustrated example spring 11 is compressed when core 2 is subject to the magnetic field generated by solenoid 4, and, when the magnetic field stops, spring 11 releases the previously accumulated energy and holds core 2 by means of a force of traction. Optionally, a second spring may be employed, operating on the other side of core 2. In such a case, the two springs 11 may simply rest on the bases of core 2, in accordance with the prior art.

The valve means are configured in a manner such as to generate a flow of fluid exiting outlet duct 10 as core 2 moves in cylinder 6. In particular, there are a first valve 12 and a second valve 14, the latter being positioned near outlet duct 10. The second valve 14 is actuated by a respective spring 15. The illustrated valves 12, 14 are non return valves. In particular, the first valve 12 is adapted to co-operate with core 2.

In particular, cylinder 6 comprises a second chamber 9, in which the fluid is intended to flow, and which is fluidically connected to work chamber 7 and to outlet duct 10. The second chamber 9 and outlet duct 10 communicate through an aperture intended to be occluded by the second valve 14. The second chamber 9 is located downstream of work chamber 7, with reference to the fluid flow. In particular, core 2 has a cavity and is associated with a tube 16 that puts work chamber 7 in fluidic communication with the second chamber 9 as the fluid flows through said cavity of core 2. Tube 16 (or at least a part thereof) is slidably and sealingly housed in the second chamber 9. In the example a gasket 19 is shown. Conveniently, the cross-section of work chamber 7 is bigger than that of the second chamber 9. In particular, said chambers 7, 9 are substantially cylindrical in shape.

As is known, core 2 defines, in work chamber 7 of cylinder 6, a pumping chamber 36 and a compensation chamber 38, which are intended to be filled with fluid. When the pump is in operation, the fluid enters work chamber 7 through inlet duct 8, then flows along tube 16 and into the second chamber 9 through the first valve 12, and finally exits through the second valve 14 and outlet duct 10. Chambers 36, 38 are generally in fluidic communication with each other, so that, during the reciprocating motion of core 2, the fluid or liquid will flow between said chambers 36, 38, thus reducing the resistance to motion of core 2. During the reciprocating motion of core 2, the volume of chambers 36, 38 varies .

By way of example, and with reference to Figure 1, the following will briefly describe the operation of the illustrated pump. When spring 11 is compressed through the effect of the magnetic field generated on core 2 by solenoid 4, the volume of pumping chamber 36 is reduced (in Fig. 1, core 2 is moving to the left), and the pressure drop generated by the expansion of the second chamber 9 opens the first valve 12, thereby causing the liquid to flow into the second chamber 9. At this stage, the compensation chamber 38 has a greater volume. When the action of solenoid 4 ends, spring 11 releases the accumulated elastic energy and pushes core 2 towards the idle position (in Fig. 1, core 2 is moving to the right), thereby increasing the volume of pumping chamber 36. At this stage, the first valve 12 is closed, and the displacement of core 2 towards the idle position increases the pressure in the second chamber 9, which causes the second valve 14 to open, thus allowing the liquid to flow out through outlet duct 10. At this stage, the compensation chamber 38 has a smaller volume.

In the example there is a tube 16 housed in an internal cavity of core 2 and rigidly constrained to said core 2. The first valve 12 is arranged inside tube 16 and includes, in particular, a shutter, in particular a ball, intended to abut on a narrower section, in particular under the action of a spring 18 constrained to one end of tube 16. As an alternative, the ball is pushed towards the narrower section under its own weight force, e.g. when the pump is tilted, in particular when said pump is arranged vertically. In particular, the narrower section is formed integrally with tube 16. In tube 16 a fluid is intended to flow. The narrower section is adapted to be occluded by the shutter, e.g. under the action of spring 18. In the particular example shown, tube 16 and core 2 are two distinct elements mechanically constrained to each other; such a solution is simple and economical to produce. In particular, tube 16 is configured in a manner such that the fluid, as it flows in said tube 16, passes from the pumping chamber 36 to the second chamber 9. Thus, the fluid cannot flow from compensation chamber 38 to the second chamber 9 through the side walls of tube 16. In fact, the side walls of tube 16 have no apertures allowing the fluid to pass directly from compensation chamber 38 to the inside of tube 16. In this case, according to one possible embodiment, chambers 36, 38 may be in fluidic communication through a channel running through core 2. Said through channel is distinct from the cavity that houses tube 16. According to further variants, core 2 and tube 16 may be made as one piece.

Optionally, a flow-rate measuring means is incorporated into said pump for measuring the flow rate of the fluid being delivered by the pump. With reference to a first embodiment, the flow-rate measuring means is located upstream of core 2, in particular upstream of work chamber 7, with reference to the fluid flow. The fluid is generally a liquid, e.g. water. In particular, the flow-rate measuring means comprises:

- an impeller 20 located between core 2 and inlet duct 8, and intended for being turned by a flow of fluid entering through inlet duct 8 and directed towards work chamber 7,

- sensing means 24 for sensing the rotation of impeller 20, for the purpose of measuring the fluid flow rate.

Preferably, impeller 20 comprises at least one magnet 22, and sensing means 24 are adapted to sense the rotation of magnet 22 in order to measure the fluid flow rate.

Sensing means 24, which may be per se known, are adapted to sense magnetic field variations caused by the rotation of impeller 20 and of magnet 22 integral therewith. For example, the sensing means may be of the electric, electronic or magnetic type, such as, for example, a magnetic sensor. Impeller 20 is adapted to rotate about an axis of rotation x-x, which is, in particular, coaxial to core 2. Impeller 20 is conveniently supported in rotation by a support 26. Support 26 may be, for example, made of ferromagnetic, in particular metallic, material; as an alternative, support 26 may be made of plastic material. Said support 26 has a pin 28 inserted in a matching recess in impeller 20 to allow rotation thereof. As can be noticed, the pump is very compact, and there is no need for a long tube connecting outlet duct 10 or inlet duct 8 to an external flowmeter, in which the fluid, e.g. water, may stagnate. This aspect is particularly advantageous in beverage dispensers, wherein it is advantageous to prevent the liquid from remaining in contact with the outside environment for long periods of time; also, this prevents undesired dripping. According to possible variants, sensing means 24 are optical ones, e.g. for reading reading portions (e.g. differently coloured stripes or other distinctive marks) on impeller 20.

Preferably, impeller 20 has only one magnet 22, the two magnetic poles of which lie in a plane transversal to axis x-x of rotation of impeller 20. This variant offers the advantage that it is both compact and inexpensive, since there is only one magnet 22. Besides, the transversal orientation of magnet 22 allows reducing the height of the impeller. Furthermore, the presence of just one magnet 22 allows reducing the revolving masses, and hence any possible vibrations .

In accordance with one possible variant, the diameter of impeller 20 is shorter than the width of work chamber 7, with reference to a plane transversal to the sliding axis of core 2. In the illustrated example, the sliding axis of core 2 coincides with axis x-x. In particular, the diameter of impeller 20 is smaller than the inside diameter of work chamber 7. In the particular embodiment shown herein, the cross-section of work chamber 7 is circular in shape. In this manner, when the pump is arranged substantially horizontally (as in Fig. 1), any air bubbles or pockets within it will not come in contact, or will only make little contact, with impeller 20, thus ensuring a more accurate measurement. In fact, air will tend to stay above the liquid (e.g. water), and when air is formed in the pump, e.g. during the initial phases of operation, the air will tend to go into cylinder 6, or will tend to remain in a region of an impeller housing chamber 30 where said impeller 20 will not touch the air or where any contact between impeller 20 and the air will be limited. Impeller 20 can thus rotate while staying immersed in the liquid.

Preferably, impeller 20 is housed in a housing chamber 30 that is fluidically connected to inlet duct 8 and to work chamber 7. The width of housing chamber 30, measured in a plane transversal to the sliding axis of core 2 (in particular, transversal to the axis of rotation x-x) , is shorter than the inside diameter of work chamber 7. In this manner, when the pump is arranged substantially horizontally (as in Fig. 1), any air bubbles or pockets within it will tend to go into cylinder 6 where core 2 slides, and therefore housing chamber 30 will remain free of air bubbles or with only a minimal quantity of air. In particular, the pump includes a cover 32 removably mounted (e.g. by means of screws 33) to cylinder 6, between which a gasket 34 is conveniently interposed. In cover 32 housing chamber 30 is formed. Housing chamber 30 is defined by cover 32 and by cylinder 6. Moreover, the illustrated cover 32 comprises inlet duct 8. Conveniently, sensing means 24 are associated with cover 32. Conveniently, inlet duct 8 is configured to direct a flow of fluid tangentially onto impeller 20, particularly onto blades of impeller 20.

In the example, housing chamber 30 fluidically communicates with the inside of cylinder 6 through at least one passage 41. In particular, said passages 41 are formed on support 26. In particular, support 26 has a substantially flat circular base, whereon passages 41 are evenly distributed .

In particular, the pump comprises the second chamber 9 fluidically connected to work chamber 7 through the first valve 12, associated with core 2. Core 2 comprises a through aperture 44 configured to allow the fluid to flow from pumping chamber 36 to the second chamber 9 only. The communication duct defined by recess 42 is separate from through aperture 44. Therefore, a part of the fluid in pumping chamber 36 flows, through the through aperture 44 and the first valve 12, into the second chamber 9; and another part of the fluid flows, through recess 42, into compensation chamber 3. With particular reference to Figure 5, the fluid flows in the communication duct defined by recess 42 in a substantially reciprocating manner (i.e. to and fro) . Generally, when core 2 moves to the right, the fluid in the communication duct defined by recess 42 will move to the left, and vice versa. The motion of the fluid through the communication duct defined by recess 42 compensates for the variation occurring in the volume of chambers 36, 38 because of the motion of the core 2. When the pump is in operation, a part of the fluid flows into said communication duct defined by recess 42.

With reference to the embodiment shown in the drawings, an inner surface of cylinder 6, which defines work chamber 7, comprises at least one recess 42 defining the communication duct. Preferably, recess 42 is substantially parallel to axis x-x. Therefore, the communication duct defined by recess 42 is substantially parallel to axis x-x. In particular, the pump includes a plurality of (in the example, two) communication channels defined by recesses 42, which are preferably distributed evenly on the inner surface of work chamber 7. In the example, the two communication channels defined by recesses 42 are located in diametrically opposite positions. In a cross-section, recess 42 on the inner surface of cylinder 6 is an open channel. In other words, core 2 and recess 42 on the inner surface of cylinder 6 create the communication duct, which is therefore a closed channel. In the particular variant shown herein, the communication duct defined by recess 42 is present along substantially the entire length of work chamber 7.

Optionally, the area of the cross-section of the communication duct defined by recess 42 is greater towards pumping chamber 36 and is smaller towards compensation chamber 38. In other words, the communication duct has a shape, possibly a tapered shape, that narrows from pumping chamber 36 towards compensation chamber 38. In this manner, a braking effect is created as core 2 moves towards compensation chamber 38, because closer the core 2 is to compensation chamber 38, the smaller the flow of fluid in the communication duct defined by recess 42; a smaller flow in the communication duct will generate a hydraulic braking effect on core 2. According to possible variants, the area of the cross-section of the communication duct defined by recess 42 is variable along its length.

Conveniently, cylinder 6 is made of plastic material. Recesses 42 defining the communication ducts are preferably made during the moulding of cylinder 6, e.g. by injection moulding. Other elements of the pump may also be made of plastic, such as cover 32, housing 40, etc.

In the particular embodiment illustrated 6 herein, core 2 conveniently has no communication channels between chambers 36, 38, and also tube 16 has no holes on its side surface. Therefore, the assembly consisting of core 2 and tube 16 is simple to manufacture, in that no complex mechanical machining is necessary. In accordance with one possible variant, core 2 further comprises a respective communication duct between chambers 36, 38.

According to possible variants, the communication duct defined by recess 42 is not straight, but, for example, at least partly curved. In addition or as an alternative, the communication duct may be at least partially inclined relative to axis x-x.

Preferably, cylinder 6 comprises, on its outer surface, a transversal protrusion 46, in particular having an annular shape, for keeping the two groups of ferromagnetic elements 5, 5' spaced apart along axis x-x. Said transversal protrusion 46 is formed integrally with cylinder 6. Transversal protrusion 46 is arranged transversally to axis x-x. Therefore, each group of ferromagnetic elements 5, 5' encircles cylinder 6 and core 2. Fig. 7 shows, by way of example, a group of ferromagnetic elements 5, 5'. The groups of ferromagnetic elements 5, 5' are therefore aligned along axis x-x of cylinder 6.

In accordance with one possible embodiment, the communication duct is a duct running through the body of cylinder 6, and communicating with pumping chamber 36 and compensation chamber 38 through first and second apertures, respectively. Therefore, only the two ends of said communication ducts face (through said apertures) into the internal part of cylinder 6 in which core 2 slides. According to this variant, the apertures may optionally be oriented at any angle with respect to axis x-x.

The present invention has some advantageous aspects also as concerns the fabrication of the pump.

In particular, according to an exemplary embodiment of the present invention, ferromagnetic elements 5, 5' are co moulded on the transversally external surface of said hollow body 6. According to an alternative embodiment of the present invention, ferromagnetic elements 5, 5' are co-moulded on the transversally internal surface of housing or reel 40 formed in solenoid 4. Furthermore, according to yet another embodiment of the present invention, ferromagnetic elements 5, 5' can be assembled without using a co-moulding process. In particular, according to an exemplary embodiment of the present invention, ferromagnetic elements 5, 5' are mounted in seats formed on the transversally internal surface of housing or reel 40 of solenoid 4. According to an alternative embodiment of the present invention, e.g. visible in Figures 8 and 9, the external surface of hollow body 6 has a transversal protrusion 46. Transversal protrusion 46 and protrusions 48 define a plurality of seats 50 in which said ferromagnetic elements 5, 5' are situated, e.g. inserted before being assembled with solenoid 4. Preferably, transversal protrusion 46 is substantially annular in shape, e.g. like a collar transversally protruding around hollow body 6. Figure 10 illustrates a variant embodiment of the transversal protrusion, designated as 146.

In the illustrated embodiment, support 26 preferably acts as a fixed core, when it is at least partly made of ferromagnetic material. In particular, the support acts as a magnetic flux conveyor, being at least partially situated in work chamber 7 (e.g. upstream of inlet chamber 36), in particular being situated upstream of piston 2. This contributes to improving the effectiveness of the positioning of recesses 42, so as to appropriately direct the magnetic flux generated by solenoid 4 to actuate piston or core 2.

Preferably, core 2 has a substantially circular cross- section. More preferably, the inner cavity of core 2 also has a substantially circular cross-section.

With reference to Figures 12 and 13, there is schematically shown a pump according to a further embodiment of the present invention.

This pump also comprises a pair of elements of ferromagnetic material 52, each one of them being situated in hollow body 6 within a longitudinal portion or tract 42a of a respective recess 42. The above mentioned longitudinal portion or tract 42 is arranged transversally between hollow body 6 and the region in which piston 2 is adapted to slide. This makes the magnetic flux that moves piston 2 more effective. Of course, in the variant embodiments including only one recess there will be a corresponding element of ferromagnetic material associated with the recess.

In particular, each element of ferromagnetic material 52 is fitted into respective recess 42, e.g. by interference, or it may be co-moulded with hollow body 6.

Preferably, each element of ferromagnetic material 52 is implemented as a small bar.

In the illustrated embodiment, the respective longitudinal portion or tract 42a, in which each element of ferromagnetic material 52 is inserted, is located upstream of hollow body 6, i.e. on the side of the fluid inlet for the pump .

According to this further embodiment illustrated herein, the communication duct that fluidically connects inlet chamber 36 and compensation chamber 38 is defined by recess 42 in a part thereof where the element of ferromagnetic material 52 is absent. In particular, said part is another longitudinal portion or tract 42b situated downstream of the longitudinal portion or tract 42a that houses the element of ferromagnetic material 52.

The pump of the present invention can be used, for example, in machines for making coffee, tea or, in general, in a machine for dispensing liquids or beverages. Besides, the pump can also be used in other apparatus, such as household appliances.

Of course, without prejudice to the principle of the invention, the forms of embodiment and the implementation details may be extensively varied from those described and illustrated herein by way of non-limiting example, without however departing from the scope of the invention as set out in the appended claims.

Claims

1. Vibration pump comprising:

- a piston (2) at least partially made of ferromagnetic material ,

- a hollow body (6) configured for being crossed by a flow of fluid and comprising a work chamber (7) in which the piston (2) can reciprocate in a guided manner, said piston (2) defining in the work chamber (7) an inlet chamber (36) and a compensation chamber (38) intended for being crossed by said fluid, wherein an inner surface of the work chamber (7) has at least one recess (42) defining at least one communication duct that fluidically connects the inlet chamber (36) and the compensation chamber (38),

- a solenoid (4) arranged around said hollow body (6) and configured for actuating the piston (2) electromagnetically, characterized in that it further comprises at least one pair of ferromagnetic elements (5, 5') arranged around said hollow body (6) and positioned transversally between said solenoid (4) and said hollow body (6); said ferromagnetic elements (5, 5') being laterally spaced apart and defining at least one perimetrical interruption (G, G') in between; said at least one recess (42) being located in said perimetrical interruption (G, G') and being laterally delimited by said perimetrical interruption (G, G') .

2. Vibration pump according to claim 1, wherein the ferromagnetic elements (5, 5') are transversally in contact with the outer surface of said hollow body (6), so that said recess (42) does not extend transversally between said hollow body (6) and said ferromagnetic elements (5, 5') .

3. Pump according to claim 1 or 2, wherein said at least one recess (42) transversally defines a respective protrusion (48) on an outer surface of the hollow body (6), and the ferromagnetic elements (5, 5') end at said protrusion (48) .

4. Pump according to any one of the preceding claims, wherein the inner surface of said work chamber (7) comprises a pair of recesses (42), each one of said recesses (42) being located in a respective perimetrical interruption (G, G') and being laterally delimited by said respective perimetrical interruption (G, G') .

5. Pump according to claim 4, wherein said recesses (42) and the respective perimetrical interruptions (G, G') are located in transversally opposite positions.

6. Pump according to claim 4 or 5, wherein the outer surface of the hollow body (6) has at least one transversal protrusion (46), said transversal protrusion (46) and said protrusions (48) defining a plurality of seats (50) in which said ferromagnetic elements (5, 5') are arranged.

7. Pump according to any one of the preceding claims, wherein the ferromagnetic elements (5, 5') are shaped like an arc of circumference.

8. Pump according to any one of the preceding claims, wherein said ferromagnetic elements (5, 5') comprise first ferromagnetic elements (5) and second ferromagnetic elements (5') axially spaced apart; said second ferromagnetic elements (5') being laterally spaced apart and defining at least one respective perimetrical interruption (G') in between, in which said at least one recess (42) is situated and laterally delimited.

9. Pump according to any one of the preceding claims, wherein said ferromagnetic elements (5, 5') are co-moulded on the transversally external surface of said hollow body (6) .

10. Pump according to any one of the preceding claims, wherein said ferromagnetic elements (5, 5') are co-moulded on the transversally internal surface of a housing (40) of said solenoid (4) .

11. Pump according to any one of the preceding claims, wherein said ferromagnetic elements (5, 5') are mounted in seats (50) formed on the transversally external surface of the hollow body (6) .

12. Pump according to any one of the preceding claims, wherein said ferromagnetic elements (5, 5') are mounted in seats formed on the transversally internal surface of the housing (40) of said solenoid (4) .

13. Pump according to any one of the preceding claims, comprising an at least partially ferromagnetic fixed core (26), which is at least partially arranged in the work chamber (7) , upstream of the piston (2) .

14. Pump according to any one of the preceding claims, further comprising at least one element of ferromagnetic material (52) situated in said hollow body (6) within a longitudinal portion or tract (42a) of said at least one recess (42); said ferromagnetic element (52) being arranged transversally between said hollow body (6) and the region in which the piston (2) is configured to slide.

15. Household appliance including a pump according to any one of the preceding claims.