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The present invention relates to a membrane pump, in particular a metering membrane pump, which allows to drastically reducing possible membrane damages during pump functioning, in a simple, reliable, efficient and economical way, increasing the pump efficiency and reducing the maintenance interventions needs.

As known, a metering membrane pump allows a transmission of the movement from a so called working fluid (contained in a working chamber, for example a hydraulic chamber wherein the working fluid is a liquid) to a so called pumping fluid (contained in the pumping chamber), while maintaining physically separated the two fluids.

The principle of the metering pump functioning, is based on the elastic deformability of the membrane which is moved by a stress exerted, in particular on the surface of the membrane facing the pump body, by a displacement fluid (for example a gaseous fluid or a liquid) contained within the working chamber. This stress may be due to mechanical phenomena, such as the action on the fluid caused by a piston movement, or pneumatic phenomena, for example by introducing and releasing the fluid (e.g. compressed liquid or compressed air) in the working chamber. The force imposed by the working fluid on the membrane surface determines the movement of the membrane and the opening and closure of suction and discharge valves, alternatively, thus creating a flow of pumping fluid from the low pressure suction line to the high pressure delivery line.

Some membrane metering pumps of the prior art, for example the pump described in the European Patent Application No. EP 1 291 524, provide the use of a membrane which abuts with a pump body wall at a suction configuration of the membrane.

However, the membrane pumps of the prior art suffer of some drawbacks.

In fact, the specific arrangement of the membrane which is positioned between the working chamber and the pumping chamber entails frequent contacts between the membrane and the walls, respectively, of the pump body and the cylinder head, facing each other, for example at each suction and/or discharge movement of the membrane.

A drawback of the membrane pumps of known type is that the frequent contact with the above mentioned terminal walls causes the rapid deterioration of the flexible surface of the membrane. In addition, the stresses due to the contact can also cause unwanted displacements of the membrane from the ideal working position.

In any case, if the membrane is damaged and/or moved from its working position, the efficiency of the pump functioning is compromised.

Therefore, the prior art membrane pumps require frequent maintenance interventions, in order to prevent possible malfunctions and in order to intervene for the replacement of the membrane. The maintenance interventions require the involvement of skilled workers with consequent high costs; an incorrect positioning of the membrane would cause an undesirable increase of the friction between the surface of the membrane and the above mentioned walls, leading to an acceleration of the membrane damage phenomena.

Therefore, the technical problem posed and solved by the present invention is to provide a metering membrane pump that allows to obviate the drawbacks mentioned above with reference to the prior art.

This problem is solved by a metering membrane pump according to claim 1. Preferred features of the present invention are shown in the dependent claims.

Advantageously, the object of the present invention allows to preserve the integrity of the membrane by means of the possibility of limiting the contact areas between the flexible surface of the membrane and the terminal walls of the pump body and the head, respectively.

A further advantage is the possibility to increase the duration of the life cycle of the metering pump, without changing the efficiency that is closely related to the structure of the deformable membrane.

A still further advantage is the possibility to facilitate the assembly of the pump and to allow simple and rapid, and therefore not expensive, installation and maintenance interventions.

Other advantages, features and the modes of employ of the present invention will become apparent from the following detailed description of some embodiments, given by way of non limiting example.

The present invention will be now described, for illustrative but not limitative purposes, according to its preferred embodiments, with particular reference to the Figures of the accompanying drawings, in which:

Figure 1 shows a side section view of a first embodiment of the membrane pump according to the invention;

Figures 2(a), 2(b), 2(c), 2(d), 2(e) show alternative forms of a detail of preferred embodiments of the membrane pump according to the present invention; Figure 3 shows a side section view of a second embodiment of the membrane pump according to the invention;

Figure 4 shows a side sectional view of a third embodiment of the membrane pump according to the invention, in particular comprising the particular of Figure 2(e);

Figure 5 shows a side section view of a fourth embodiment of the membrane pump according to the invention;

Figure 6 shows a side section view of a fifth embodiment of the membrane pump according to the invention;

Figure 7 shows a side section view of a sixth embodiment of the membrane pump according to the invention;

Figure 8 shows a side sectional view of a seventh embodiment of the membrane pump according to the invention;

Figure 9 shows a side sectional view of an eighth embodiment of the membrane pump according to the invention;

Figure 10 shows a side sectional view of a ninth embodiment of the membrane pump according to the invention;

Figure 11 shows a side sectional view of a tenth embodiment of the membrane pump according to the invention.

In the Figures identical reference numbers will be used for similar elements. In the following description, the directional terminology, such as "right", "left", "front", "rear", "base", "top", "upper", "lower", "side", etc., is used with reference to the Figures of the accompanying drawings. Since components and/or elements and/or embodiments of the present invention can be positioned and/or operated in various different orientations, the directional terminology is used purely by way of example and not of limitation.

With reference to Figure 1, it can be seen that a first embodiment of the membrane pump

100 according to the invention, in particular a metering pump, comprises a head 5 and a pump body 6. As illustrated, the head 5 comprises a distribution chamber 15, which is shaped to allow the sliding of an operating fluid from a suction valve 1 to a delivery valve 2. In particular, in the first embodiment, the distribution chamber 15 comprises a suction channel and a delivery channel which, starting from the respective valves, flow into a pumping chamber L, as will be detailed below.

As shown in Figure 1, the pump body 6 and the head 5 are coupled to each other at a coupling surface S, for example, an annular coupling surface, to delimit the pumping chamber L between an terminal wall 36 of the body pump 6 and a further terminal wall 35 of the head 5.

A membrane 4 is placed, or positioned, in the pumping chamber L, at the aforesaid coupling surface S and is configured to separate the working chamber 16 from the distribution chamber 15. The membrane 4 is shaped to be moved, within the pumping chamber L, by means of a fluid contained in the working chamber 16. In particular, the membrane is moved by a pressure variation produced inside the working chamber 16 that may occur due to mechanic way, for example by the movement of a piston 3 - as shown in Figure 1 - or pneumatic way, for example introducing and releasing, alternately, compressed air in the working chamber 16.

The pressure variation imposed by means of the fluid inside the working chamber 16 determines the movement of the membrane from a suction configuration, wherein it is advantageously arranged in the proximity of - and not in contact with - the terminal wall 36, to a delivery configuration, wherein it is arranged in the proximity of (and possibly not in contact with) the above mentioned terminal wall 35. In Figure 1, the membrane 4 is shown in the suction configuration.

The membrane 4, for example made of elastic material, is shaped to allow the transmission of the movement from the fluid contained in the working chamber to the fluid contained in the pumping chamber, keeping the two fluids physically separated.

Advantageously, the membrane pump 100 according to the invention comprises a sealing device 7 coupled, or couplable, to the membrane 4 configured to abut with an outlet mouth 26 of the working chamber 16 at the suction configuration, in a manner such that to seal the area C comprised between the membrane and the pump body with respect to the working chamber 16, as will be detailed below. In addition, or alternatively, the sealing device 7 is configured to abut with an inlet mouth 25 of the distribution chamber 15 at the membrane delivery configuration, in such a way as to seal an area C comprised between the membrane and the head with respect to the distribution chamber 15, as will be detailed below.

In the first embodiment here described, the sealing device comprises an element shaped as a disc 7 fixed to the membrane 4, in particular fixed at a central region of the membrane.

As shown in Figure 1, the disk 7 is positioned on the face of the membrane that is faced towards the terminal wall 36 of the pump body 6, in an assembly configuration, and is fixed to the membrane 4, for example during a production or moulding phase of the membrane.

In particular, in the embodiment shown in Figure 1, the disc 7 is thickened in such a way as to ensure a spacing of the membrane 4 from the terminal wall 36.

Optionally, the disc 7 is made of a metallic material or of a thermosetting polymeric material in such a way as to ensure the stability and the maintenance of the original shape of the disc, both during use and during a possible making process of the membrane.

For example, in a making phase of the membrane in plastic material through a moulding process, the plastic material penetrates during the process of realization in special slits present along the disc thickness. In particular, the disc 7 and the membrane 4 are fixed to each other, in an irreversible manner.

Alternative embodiments of the fastening of the disc 7 to the membrane 4 are provided, for example, a mechanically coupling between two disc elements 7 respectively positioned on opposite faces of the membrane 4 previously realized, is provided.

As shown in Figures 1 and 2(a), 2(b), the thickened disc 7 has a distal terminal portion, for example a base facing the pump body 6, which is shaped in such a way to completely cover the outlet mouth 26 of the working chamber 16. In particular the distal terminal portion of the disc 7, optionally a substantially planar base, has an edge 27 shaped to abut, optionally by means of a shape coupling, with an edge of the outlet mouth 26 of the working chamber 16.

In other embodiments not shown, the desired spacing may be achieved by a suitable shape of the outlet mouth 26. For example, by means of a thickening of the edge of the outlet mouth, or a projection at the outlet edge, an abutment with the edge of the disc 7can be guaranteed, in particular to establish a sealing zone as will be described in more detail below.

As shown in Figure 1, 2(a) and 2(b), the edge 27 has a relief pattern configured to be coupled to a corresponding relief pattern provided on the edge of the outlet mouth 26. In the example shown, these relief patterns are tilted by 45° with respect to a longitudinal axis of the disc 7 and oriented in a manner such as to allow the coupling between the distal end of the disc 7 and the outlet mouth 26. Alternative embodiments include other coupling typologies between the disc 7 and the edge of the outlet mouth, for example other coupling conformations between the parts. The placement of a gasket, or of an alternative sealing element between the parts, is also provided to ensure the realization of a sealing area.

In the described example, the coupling between the edge of the outlet mouth 26 and the upper edge 27 of the disc 7 provides a sealing front with respect to the fluid located in the working chamber 16.

Advantageously, the specific mounting configuration of the membrane 4 allows the realization of a first interspace C between a membrane surface and the terminal wall 26 of the pump body 6 when the membrane assumes the suction configuration. The interspace C is configured to space at least a bending portion F of the membrane 4 by at least one wall of the pumping chamber L. In particular, the bending portion F is defined as the portion of the membrane 4 comprised between the sealing device, which is fixed at a central region of the membrane, and the membrane edge which is fixed to the pumping chamber at the coupling surface S. For example, the bending portion F is the portion of the membrane which - during an operating condition of the pump - is exposed on both sides, respectively, to the working fluid and to the pumping fluid,.

As shown in Figure 1, at the suction configuration, the membrane 4 is located in the proximity of and not in contact with the terminal wall 36.

The advancement of the membrane 4 towards the working chamber 16 is stopped by interference between the edge 27 of the disc 7 and the edge of the outlet mouth 26. In particular, the interference provides the realization of a sealing face, therefore, a portion of the fluid contained in the interspace C cannot forced out from the interspace at least until the membrane 4 is stressed in the opposite direction towards the delivery configuration.

In the example described in Figure 1, the thickness of the disc 7 determines a maximum height of the interspace C. Advantageously, at a suction configuration, the membrane 4 does not interfere with the wall 36 of the pump body because it is supported by the fluid contained in the interspace C.

Therefore, the interspace C is shaped to space at least the bending portion of the membrane 4 from the terminal wall 36 by providing a system for controlling, preventing and preserving the integrity of the membrane 4. The interspace C realization makes it possible to control the maximum extension of the flexible portion of the membrane 4, thus allowing to prevent and reduce any damage of the membrane 4.

In general, the specific conformation of the interspace C, which can vary for example depending on the shape of the reference terminal wall, the thickness of the disc 7 and/or depending on the thickness of the edge of the outlet mouth 26, can be suitably sized depending on the elasticity degree of the specific membrane 4, and then depending on the value of maximum extension that the membrane 4 can reach at the suction configuration.

Optionally, the volume of the interspace C is minimized, so as to ensure the necessary support to the membrane 4 and at the same time to minimize the amount of fluid contained in the interspace C so as to limit possible constructional problems deriving from the management of fluidodinamic processes into the interspace C volume (for example, problems due to the reaching of high pressures and/or the realization of air bubbles in the case in which a liquid is used as the process fluid).

Advantageously, the interspace C has a hydraulic function of separation (or fluid function, for example in the case of air pumps) which is realized when the membrane assumes one of the two suction or delivery configurations, regardless of the specific operating conditions of the pump . In particular, the hydraulic effect of separation is also achieved in the stop condition of the pump, in operating conditions with low or negative suction pressures (as well as with high pressure), or in safe operating conditions, for example conditions determined by the activation of a safety valve (internal or external) that involves rapid pressure value changes on the membrane, both during suction and during delivery.

In the example here described, a disc 7 can be fixed in different ways on a membrane so as to determine a different degree of maximum extension at the suction configuration.

As shown in Figures 2(a) and 2(b), a thickened disc 7 can be fixed to the membrane 4 at a base surface or at a centreline portion of the disc. The configuration shown in Figure 2(b) is for example applicable to a membrane made of material more rigid and less deformable than the membrane used for the configuration of Figure 2(a). Therefore, in the case of a membrane made of material more rigid and less deformable, a lower thickness of the interface it is sufficient to preserve the membrane from wear and damage phenomena that would result from undesired contact with the terminal wall 36.

As shown in Figures 2(c) and 2(d), a further sealing device 70 can be obtained by assembling together multiple components, for example by coupling a thickened disc 7' or 7", respectively, to a spacer element 77' or 77" through a tongue and groove coupling, in particular by means of a threaded coupling. The spacer elements 77' and 77" are shaped to limit, or maintain below a maximum extension limit of the membrane, a membrane 4 stroke from the suction configuration to the delivery configuration.

Moreover, the spacer elements are used to change the volume of the interspace C and to adapt it to the requirements of the specific case (for example, to manage fluid dynamic processes, as described above).

In a first embodiment of the present invention, the terminal wall 36 of the pump body 6 has a tapered shape from an outer edge of the wall, for example in the proximity of the coupling surface S, towards the outlet mouth 26 of the working chamber 16, in order to ensure the desired spacing with respect to the bending portion F of the membrane 4. In the example shown in Figure 1, the terminal wall 36 is shaped as a conical surface portion. In general alternative conformations of the end wall 36 are provided, for example, variable according to the pump operating parameters, the working fluids used, the configuration of the sealing device 7 and the membrane 4 used.

By way of non limiting example, the terminal wall 36 of the pump body 6 may have a concave surface, in particular at a portion which extends from the coupling surface S towards the outlet mouth 26 of the working chamber 16.

Figure 3 shows a second embodiment of the membrane pump 100 according to the invention in which a further abutment surface is provided inside the working chamber 16 and the sealing device 7 is shaped in such a way as to restrict a movement of the membrane 4 towards the distribution chamber 15 during a delivery phase of the working fluid B. In particular, the disc 7 comprises a further spacer element mounted to interfere on the further abutment surface provided in the working chamber 16 in such a way as to limit the maximum extension of the membrane 4 into the delivery configuration.

In Figure 2(e) an enlarged detail of Figure 4 is shown, relative to a sealing device 70 comprising a disc 7"' elastically coupled to a spacer element 77"' by means of a spring 29. The sealing device 70 of Figure 4, which essentially works as a multi-valve device, is shaped to limit the losses of fluidodinamic load of the working fluid B by means of an increasing of the passage surface of the fluid. During a working phase of the pump, both during the delivery and the suction phase, the working fluid B also passes through the channels 109 provided on the surface of the spacer 77"'. Therefore, at equal flow rates, the fluid velocity decreases resulting in an advantageous reduction of the load losses.

In particular, the spring 29 is configured to maintain the disc 7"' in a configuration substantially spaced apart by the element spacer 77"' during the delivery phase of the pump. The working fluid B therefore remains fluidodinamically-connected to the interface C until the suction phase, in correspondence of which the disc 7"' is positioned in abutment on the spacer 77"' by closing a passage for the working fluid B. In this suction position, the interspace C exerts the desired support of the entire bending portion of the membrane 4. In Figure 5 is shown an alternative embodiment of the sealing device 70. As for the configuration of Figure 4 detailed in Figure 2(e), the sealing device 70 in Figure 5 comprises a disc, which abuts on a spacer element positioned at the outlet mouth 26 of the working chamber 16. As already described in relation to Figure 4, also the embodiment shown in Figure 5 it allows to reduce the load losses of the working fluid B, increasing the surface useful for the fluid passage in a working condition of the pump.

In general, as shown for example in Figure 6, in order to improve the functioning, the membrane 4 is pretensioned in the direction of the working chamber 16 in a manner such as to guarantee a more efficient response to the solicitation of the motion of the working fluid B.

Advantageously, the pretensioning of the membrane contributes to maintaining the coupling between the edge 27 of the disc 7 and the outlet mouth 26 of the working chamber 16 that ensures the creation of the interspace C.

A further embodiment of the pump according to the invention provides that the pretensioning of the membrane, optionally made of metallic material, is made at the time of assembly of the membrane. The membrane can then be fixed at their edges to the coupling surface S in a pretensioned configuration. In particular, the membrane 4 according to the present invention can be made in PTFE, and/or rubber and/or a metallic material and/or plastic material.

Advantageously, the membrane made of metallic material resists to very high working pressures, for example, allows to work with pressure differences of thousands of bar between the working fluid B and the pumping fluid A (wherein 1 bar = 100 kPa).

The membranes made of plastic material do not maintain the pretensioning provided in the assembly phase, contrary to what happens to the membranes made of metallic material.

The use of elastic means, for example a spring as shown in Figure 6, is provided in order to ensure the pretensioning of the membrane 4. In particular, the spring can be of the helical type, or for example a cup spring, or an electromagnetic spring.

In particular, the membrane 4 is preloaded by a force in the direction of the working chamber 16, having an intensity such as to create inside the working chamber a pressure higher to the pressure in the distribution chamber, optionally at least 1 bar higher. Therefore, through the preload of the membrane 4, an artificial pressure in the chamber 16 is created so as to avoid cavitation phenomena of the working fluid.

Further embodiments of the membrane pump 100 according to the present invention provide the use of actuating means for adjusting the intensity of the preload of the membrane 4. For example actuator means of mechanical and/or hydraulic and/or gas and/or electric and/or magnetic type.

In the case in which the metering pump involves the use of a multiple membrane, a fixing of the above mentioned sealing device to at least one of the membranes is provided, independent from the specific positioning. Namely, depending on the specific requirements, the sealing device can be applied on the membrane facing towards the working chamber 16, or on the membrane facing towards the distribution chamber 15, or on both the membranes. For example, in Figures 7 and 8 a double membrane pump with interposed fluid and a double membrane pump with interposed empty are, respectively, provided. A still further alternative embodiment of the pump according to the present invention, not shown in the figures, provide the use of a plurality of membranes mounted in series, for example three membranes. In the case in which also a central membrane is provided with a sealing disc 7, the realization of a further fluid interspace defined between two consecutive membranes will be possible.

Advantageously, the sealing device 7 of the metering pump according to the present invention supports the membrane 4 and allows the restoration of the correct amount of working fluid (between the membrane and the piston), for example by increasing or decreasing the amount of working fluid independently of the working pressure, in case of sudden loss of fluid in one of the two sides (for example, following the intervention of a overpressure valve, or in the case of not perfect sealing of one or more of the valves provided in the pump).

Advantageously, the metering membrane pump according to the present invention allows the monitoring of the proper amount of working fluid by means of a hydraulic system, or by means of a mechanical and hydraulic system wherein the pump driving is actuated by the detection of a specific positioning of the membrane. For example, in the embodiment shown in Figure 9, the recovery valve of the working fluid is mechanically actuated only after a detection of a correct positioning of the membrane 4. In particular, the amount of liquid (for example oil) between the piston and membrane is controlled by means of the rearward position of the membrane, such detection mechanically actuated allows the opening of a central duct of the valve for the liquid to restore.

In Figure 10 a ninth preferred embodiment of the pump 101 according to the present invention is shown, wherein the disk 7 is positioned on a face of the membrane 4 facing towards the distribution chamber 15. For example, the distribution chamber 15 is shaped as a straight duct between the suction valve 1 and the delivery valve 2. On a side surface of the straight duct the inlet mouth 25 of the distribution chamber 15 is positioned. The thickened disc 7 has a portion of distal end, for example a base facing the head 5, which is shaped in such a way as to completely cover the inlet mouth 25 of the distribution chamber 1. In particular, the distal end portion of the disc 7, optionally a substantially planar base, has an edge 47 shaped to abut, optionally in a shape coupling way, with an edge of the inlet mouth 25 of the distribution chamber 15.

For example, the edge 47 has a relief pattern configured to be coupled to a corresponding relief pattern provided on the edge of the inlet mouth 25, in particular such relief patterns are tilted by 45° with respect to a longitudinal axis of the disc 7 and oriented in a manner such as to invite the coupling between the distal end of the disc 7 and the inlet mouth 25.

The coupling between the inlet mouth 25 and the edge 47 creates a sealing face with respect to the fluid located in the distribution chamber 15.

The specific mounting configuration of the membrane allows the realization of a second interspace C between a bending portion of the membrane and the terminal wall 35 of the head 5. Therefore, advantageously, the bending portion of the membrane is supported from the fluid interspace C and so it is not in contact with the terminal wall of the head 5, extremely increasing the product life cycle of the membrane.

In Figure 11 a tenth embodiment of the pump 101 according to the invention is shown, wherein the disc 7 is shaped in such a way as to be fixed to the membrane at at least a centreline portion and has two protruding portions on the two faces of the membrane, respectively facing towards the body pump 6 and the head 5. In particular, this embodiment allows the realization of a first interspace C at an inlet configuration of the membrane 4 and a second interspace C" at a delivery configuration of the membrane, thus avoiding that the membrane contacts the terminal wall 35 of the head 5, especially in the case in which it is subjected to high stress during the discharge phase of the pump, maximizing the prevention of possible damage on both sides of the membrane. Advantageously, the terminal wall 35 of the head 5 can have a tapered shape, for example comprising at least a conical portion, starting from an outer edge of the wall (for example corresponding to the coupling surface S) towards the inlet mouth 25 of the distribution chamber 15.

As already illustrated for the terminal wall 36 of the pump body 6, the terminal wall 35 may present a plurality of conformations, also different from the conformations shown in the Figures described herein, for example, variable according to the pump working parameters, to the working fluids used, to the configuration of the sealing device 7 and the membrane 4 used. In the above preferred embodiments have been described and variants of the present invention have been suggested, but it is to be understood that the skilled in the art can make modifications and changes, without so departing from the related scope of protection, as defined by the attached claims.