Water storage tank and pump with such tank

Abstract

The present invention relates to a water storage tank including at least one first portion and at least one second portion under the same pressure as the stored liquid. The first portion and the second portion each define an elastically variable water storage volume. A first elastic resistance device that resists expansion of the corresponding water storage volume is associated with the first portion of the water storage chamber, and a second elastic resistance device that resists expansion of the corresponding water storage volume is associated with the second portion of the water storage chamber. Thus, when the pressure of the liquid in the tank increases, the stored volume expands against the resistance of the respective elastic resistance device, and when the pressure of the liquid in the tank decreases, the stored volume contracts. Each of the elastic resistance devices has a primary direction of resistance to expansion. The two elastic resistance devices are positioned opposite each other, and their respective primary directions of resistance to expansion are opposite to each other.

Description

[Technical Field]

[0001] The present invention relates to the field of hydraulic fluid management, and more particularly to reservoir tanks preferably, but not exclusively, used with hydraulic pumps.

[0002] The present invention also relates to a hydraulic pump having such a water reservoir. [Background technology]

[0003] Hydraulic pumps of the "pressure tank" type, i.e. systems for obtaining water pressures higher than those in the water distribution network (or reservoir), have been known for many years, allowing the delivery of drinking water to high or distant use equipment.

[0004] A pressure tank system includes a hydraulic pump, typically a centrifugal pump, and a reservoir tank at its delivery end. Associated with the pump is a pressure switch that controls the pump to switch on or off at a given delivery pressure or pressure downstream of the pump towards the equipment being used.

[0005] The reservoir is nothing more than a water reservoir divided into two parts by a membrane. The lower part of this reservoir contains water at the pump's delivery pressure, and the upper part contains air at a given pressure that acts as an elastic spring for the water on the delivery side. When the system is under operating pressure and the pressure detected by the pressure switch drops slightly below a threshold (for example due to a small leak in the system or very short use by the equipment used), the pump will start to bring the delivery pressure (or system pressure) back up to a predetermined optimum value (actually the system's working pressure), at which point the pump will stop again. This prevents the pump from continuously "starting and stopping" for small pressure drops between the predetermined optimum value and the threshold under pressure on the pump's delivery side.

[0006] When the pump is operating to restore pressure in the system (the device is closed), the tank membrane deforms, expanding the volume at the bottom of the reservoir, and the pumping pressure fills the reservoir with water. When a slight pressure drop occurs, the air acts as a spring, causing the membrane to deform in the opposite direction, or the volume occupied by the water to contract.

[0007] If a large volume of water is demanded by a use, such as that controlled by a pressure switch, flow switch, or pressure-flow switch, or if a more sudden and significant drop in pressure occurs, the pump will operate until the use is closed.

[0008] A problem associated with known types of reservoir pumps is that the air chamber of the tank must be adjusted to ensure a suitable operating range for the pump for each particular condition of use.

[0009] Figure 1 shows a graph of the hydraulic head of a pump as a function of flow rate, associated with the characteristic curve n of a pressure-tank pump with an attached reservoir. Consider a pump that needs to operate at approximately 4.5 bar (approximately 45 meters of head). The reservoir of the pressure tank must operate within a pressure range from P1, corresponding to 3.5 bar (approximately 35 meters of head), to P2, corresponding to 5.2 bar (approximately 52 meters of head). Here, P1 represents the pressure value below which the pump's pressure switch activates the rotation of the pump's impeller, and P2 represents the reservoir's operating pressure. When the reservoir's operating pressure value is reached, the pump stops pumping. After installing the pump, the installer must adjust the amount of air in the reservoir between the membrane and the reservoir to allow operation within the above range.

[0010] As shown in the characteristic curve in Figure 1, pumps can operate outside of their specified full head range. Each time a pump is installed in a system, the installer must adjust the amount of air in the tank to achieve the desired membrane resistance in the reservoir. This adjustment necessarily increases the installation time of the pump.

[0011] Also, over time, air may escape from the reservoir, causing the pump's operating range to become unregulated. Therefore, the correct amount of air in the tank must be readjusted periodically.

[0012] Additionally, these reservoirs are oversized to withstand water hammer that occurs within the system.

[0013] Also, the water stored in these reservoirs tends not to be completely drained, leaving a certain amount of water remaining in the reservoir, which can create problems with bacterial growth.

[0014] In particular, the use of such a water reservoir also typically leads to a very bulky system configuration.

[0015] To overcome these problems, European Patent Application No. 4015826 describes a hydraulic pump equipped with an integrated water storage tank containing multiple water storage chambers. Each chamber has a water storage volume that can expand based on the pressure of the stored liquid. Each chamber is equipped with an elastic spring device that suppresses the expansion of the chamber. The stiffness of the springs in each chamber varies, resulting in different chamber expansions. This allows the pump to be used in a variety of operating situations. In practice, each water storage chamber has its own expansion resistance device with its own stiffness, allowing the pump to operate over a predetermined pressure range. In practice, the pump includes a water storage tank (chamber) that is already calibrated (during pump assembly or design), so the pump can simply be placed in the system without adjusting any elements of the tank.

[0016] Although the above-mentioned solutions are particularly advantageous, they do not lend themselves to improvements, in particular to further reducing the size of the various components. Summary of the Invention [Problem to be solved by the invention]

[0017] It is therefore an object of the present invention to provide a water tank that can be integrated into a hydraulic pump and that solves the problems associated with installing and using the pump in a system for increasing the pressure of drinking water to a water distribution network or a water tank.

[0018] Within this objective, an important object of the invention is to produce a water tank that can be easily installed on a pump, for example for a system for increasing the pressure of drinking water.

[0019] Another important object of the present invention is to produce a water storage tank that eliminates the need for adjustments to the tank during installation.

[0020] Another important object of the present invention is to produce a water storage tank that requires less pump maintenance.

[0021] Yet another important object of the present invention is to produce a particularly compact water storage tank. [Means for solving the problem]

[0022] These and other objects, which will become more apparent below, are achieved by a water storage tank including at least one first portion and at least one second portion under the same pressure as the stored liquid. The first and second portions each define an elastically variable water storage volume. A first elastic resistance device, which resists expansion of the corresponding stored volume, is associated with the first portion of the water storage chamber, and a second elastic resistance device, which resists expansion of the corresponding stored volume, is associated with the second portion of the water storage chamber. Thus, when the pressure of the liquid in the tank increases, the stored volume expands against the resistance of the respective elastic resistance device, and when the pressure of the liquid in the tank decreases, the stored volume contracts. Each of the elastic resistance devices has a primary direction of resistance to expansion. The two elastic resistance devices are positioned opposite each other, and their respective primary directions of resistance to expansion are opposite to each other. The fact that the water storage tank comprises at least one first portion and at least one second portion of the water storage chamber arranged to be under the same pressure as the stored liquid essentially means that the at least one first portion and at least one second portion of the water storage chamber are adapted to contain the stored liquid and that in these chambers the liquid contained therein is under the same pressure.

[0023] According to one aspect, the present invention relates to a water storage tank including at least one first water storage chamber and at least one second water storage chamber under the same pressure as the stored liquid. The first water storage chamber and the second water storage chamber each define an elastically variable water storage volume. A first elastic resistance device is associated with the first water storage chamber, resisting expansion of the respective water storage volume, and a second elastic resistance device is associated with the second water storage chamber, resisting expansion of the respective water storage volume. Thus, when the pressure of the liquid in the tank increases, the water storage volume expands against the resistance of the respective elastic resistance device, and when the pressure of the liquid in the tank decreases, the water storage volume contracts. Each elastic resistance device has a main direction of resistance to expansion. The tank is characterized in that the two elastic resistance devices are arranged opposite each other, and their main directions of resistance to expansion are opposite to each other. The fact that the first chamber and the second chamber are arranged to be under the same pressure as the reservoir liquid essentially means that the first reservoir chamber and the second reservoir chamber are adapted to contain the reservoir liquid and the liquid contained in these chambers is under the same pressure.

[0024] Preferably, the principal directions of resistance to expansion of the elastic resistance devices on both sides are substantially opposite and coincident with each other on a single axis of action.

[0025] According to a preferred embodiment, a first resistance device associated with the first water storage chamber is at least partially disposed within a second resistance device associated with the second water storage chamber.

[0026] According to a preferred embodiment, each of the elastic resistance devices comprises: a movable element adapted to move at least partially from a first position corresponding to a minimum volume that can be occupied by the liquid in the chamber to a second position corresponding to a maximum volume that can be occupied by the liquid in the chamber; a resilient resistor adapted to provide a resilient resistance to movement of the movable element from the first position to the second position; Includes:

[0027] Preferably, the elastic resistor is disposed outside the water storage chamber between the movable element and the abutment stopper, and is configured to compress in a direction from the movable element to the abutment stopper.

[0028] According to a preferred embodiment, the elastic resistor of the first elastic resistance device associated with the first water storage chamber is located primarily within the space occupied by the elastic resistor of the second elastic resistance device associated with the second water storage chamber. Preferably, the elastic resistor is an axial spring, preferably a helical spring, preferably a cylindrical spring.

[0029] According to a preferred embodiment, the movable element of the first elastic resistance device is adapted to slide within an axial channel defined in the movable element of the second elastic resistance device, or vice versa, the movable element of the second elastic resistance device is adapted to slide within an axial channel defined in the movable element of the first elastic resistance device.

[0030] According to a preferred embodiment, at least one movable element is integral with or forms a wall portion of the water storage chamber, and movement of at least a part of the movable element allows the volume of the water storage chamber to expand. Preferably, the direction of movement of at least a part of the movable element coincides with the main direction of resistance to expansion of the respective water storage chamber.

[0031] According to a preferred embodiment, each of the water storage chambers has a first chamber portion with a fixed volume and a second chamber portion with a variable volume defined by the movement of a movable element of the respective elastic resistance device.

[0032] Preferably, the movable element comprises a membrane sealed and connected to the first chamber portion, and a slider fixed to the membrane, the slider adapted to interact with an elastic resistor to allow movement of a portion of the membrane to vary the volume of the chamber.

[0033] According to a preferred embodiment, an outer casing is provided that defines a central housing. Closure lids are secured to opposite ends of the housing, thereby defining a first water storage chamber and a second water storage chamber at the closed ends. The first and second elastic resistance devices are disposed within the central housing and adapted to provide resistance in opposite directions to each other.

[0034] According to a preferred embodiment, for each of the chambers, a respective lid defines a first chamber portion, at least one passage is defined on the lid for ingress / egress of the reservoir liquid, and the passages of the first chamber and the second chamber are under the same pressure.

[0035] Preferably, the tank has a modular structure with at least one module, each of which includes a central housing with two water storage chambers on either side. If there are at least two modules, the housings of the modules have central axes that are parallel and aligned with each other. Preferably, adjacent water storage chambers of two adjacent modules have the same lid.

[0036] According to a preferred embodiment, for a given pressure value in the water storage chambers, at least one first elastic resistance device is associated with a first volume change in the corresponding at least one first water storage chamber, and at least one second elastic resistance device is associated with a second volume change in the corresponding at least one second water storage chamber. The first volume change and the second volume change are different from each other. That is, the at least one first elastic resistance device and the at least one second elastic resistance device are configured to allow different water storage volumes in the at least one first water storage chamber and the at least one second water storage chamber, respectively. Preferably, for a given pressure value, the elastic resistance devices are configured to allow different water storage volumes in all water storage chambers.

[0037] According to a preferred embodiment, the at least two elastic resistance devices have different elastic stiffnesses.

[0038] According to a preferred embodiment, all reservoir chambers have the same minimum and maximum volume that the liquid can occupy.

[0039] According to a preferred embodiment, at least two, and preferably all, of the water storage chambers have a first chamber portion with a fixed volume and a second chamber portion with a variable volume defined by the movement of a movable element. The fixed volume of the first chamber portion is the same for at least two water storage chambers. The at least two water storage chambers are associated with elastic resistors with different stiffnesses, which allow the chambers to expand differently, so that when the pressure of the liquid in the at least two water storage chambers is the same, the chambers can have different volumes.

[0040] According to another aspect, the present invention relates to a hydraulic pump, comprising a path for liquid from at least one suction port for liquid in the hydraulic pump to a delivery port for liquid from the pump, and along the path: a pressure section downstream of the suction port configured to increase the pressure of the liquid; a reservoir for pressurized liquid downstream of the pressurization section, as claimed in one or more of the preceding claims, the separate reservoir chambers all being under the same liquid delivery pressure; will be established.

[0041] Preferably, the hydraulic pump includes an outer casing having a passage defined therein for the liquid, and having therein: a bay for accommodating at least one impeller of the pump; a space for liquid under the delivery pressure of the pump on one side of the compartment so as to develop substantially following the development of the axis of rotation of the at least one impeller; is provided. The water storage chamber of the tank is in direct communication with the space. Preferably, the direction of action of the elastic resistance device is perpendicular to the axis of the pump motor. Preferably, a base plate for the pump is provided on the opposite side of the compartment, whereby the space is located above the compartment. Preferably, a liquid delivery outlet is provided in the space.

[0042] According to another aspect, the hydraulic pump is an axially deploying submersible pump, and the at least one tank is disposed within the casing of the pump and has an action axis of the elastic resistance device that deploys parallel to the axial deployment axis of the submersible pump.

[0043] The hydraulic pump may include an electronic control unit operatively connected to an electric motor that drives a pressure member in the pressurizing section of the pump, and a pressure gauge, preferably a pressure switch, adapted to measure the pressure in the region between the liquid delivery section and the delivery outlet, whereby the electric motor is adapted to activate the pressure member when a first pressure value measured by the pressure gauge is reached, and to interrupt the operation of the pressure member when a second pressure value measured by the pressure gauge, the second pressure value being greater than the first pressure value, is reached. [Brief explanation of the drawings]

[0044] The present invention will be better understood with reference to the following description and the accompanying drawings, which set forth some non-limiting examples of embodiments of the invention. [Figure 1] 1 is a total head / flow graph showing the characteristic curve of a general-purpose hydraulic pump with an expansion tank according to the prior art, where the pressure range over which the pump operates is highlighted. [Figure 2] 1 is a schematic diagram showing a cross section along the longitudinal axis of a pump according to the present invention; [Figure 3] 3 is a top view of the pump of FIG. 2, showing a cross section of the reservoir tank along a horizontal plane passing through the axis of the reservoir tank; [Figure 4] 4 is a schematic axial cross-sectional view of the tank of FIG. 3 according to the present invention; FIG. [Figure 5] 1 is a schematic diagram of a variant of a pump having a tank with two modules according to the invention, where a cross section of the pump is shown along a horizontal plane passing through the axes of the two modules. [Figure 6] 1 is a top view of a variant of the pump according to the invention, which differs from the embodiment of the previous figures in that the cross section of the reservoir tank is shown along a horizontal plane passing through the tank axis, where the tank is in a minimally or not at all expanded state; [Figure 7] A cross section of the tank in Figure 6 along a horizontal plane passing through the axis of the tank is shown, where the tank is fully inflated. [Figure 8] 1 is a total head / flow rate graph showing a characteristic curve of a hydraulic pump according to the present invention. [Figure 9] 1 is a schematic diagram of a submersible pump with axial development including a tank according to the present invention; FIG. DETAILED DESCRIPTION OF THE INVENTION

[0045] Referring to the aforementioned figures, a hydraulic pump with tank according to the present invention is generally designated by the reference numeral 100.

[0046] The pump 100 includes an outer casing 101 that defines an inlet 102 for liquid within the pump and an outlet 103 for liquid from the pump.

[0047] A path P for liquid is provided within the outer casing 101, extending from the suction port 102 to the delivery port 103 (schematically shown by a broken line in FIG. 2).

[0048] Along the path P in the casing, downstream of the suction port 102, there is provided a pressure section 104 configured to increase the pressure of the liquid. The pump therefore includes, in order, a suction section provided with the suction port 102, a pressure section 104, and a delivery section provided with the delivery port 103.

[0049] In particular, in this embodiment the pump is a multi-stage centrifugal pump (in other embodiments the pump may be single-stage or non-centrifugal), and therefore the pressure section 104 has a plurality of impellers, generally designated 105, mounted on a shaft having an axis of rotation X.

[0050] More specifically, the casing 11 includes a first compartment 106 in which the impeller 105 is arranged, and a second compartment 107 arranged contiguous to the first compartment 106 along the rotation axis X and in which an electric motor 108 for rotating the impeller 105 is arranged.

[0051] On the outside of the outer casing 101, a base plate 101.1 for the pump is provided, so that the pump preferably operates with its axis of rotation X parallel (or nearly parallel) to the surface on which the pump base plate rests. The pump can also operate arranged on a support surface with its axis of rotation X perpendicular or nearly perpendicular to the support surface. In fact, it can operate at any position in space.

[0052] Along the path P, downstream of the pressurized section 104 (ie, upstream of the outlet 103), there is a space 109 in which the liquid is under substantially the same pressure as the outlet 103, ie, the outlet pressure.

[0053] In particular, for example, this space 109 is provided on the side of the first compartment 106 opposite to the side of the first compartment on which the base plate 101.1 is provided, so that the space 109 is located above the first compartment 106.

[0054] It should be noted that this space 109 has a greater longitudinal extension, for example to follow the extension of the impeller's rotation axis X. In other embodiments, the space 109 can be replaced by one or more channels, all under the same delivery pressure as the delivery outlet 103.

[0055] Also arranged along the path P, downstream of the pressurizing section 104, is a storage tank 10 for pressurized liquid, which has an elastically variable storage volume and an elastic resistance system that limits the expansion of the storage volume in response to an increase in pressure within the tank.

[0056] Advantageously, the water storage tank 10 has, for example, a modular structure, where each module M has a first and second water storage chamber portion, which in this embodiment are made up of two separate water storage chambers 20 and 30 located opposite each other. Figures 2 and 3 show an example of a single module M. Figure 5 shows an example of two modules arranged side by side, for a total of four water storage chambers. Figures 6 and 7 show an example of a second embodiment of each module, with a single water storage chamber formed by first and second portions located opposite each other, as will be described in more detail below.

[0057] Referring to Figures 2-5, the reservoir chambers 20 and 30 are all under the same pressure of reservoir liquid corresponding to the delivery pressure of the pump 100 (this is true for a single module M having two chambers as well as for multiple modules M having multiples of two chambers).

[0058] Each reservoir chamber 20 and 30 defines a respective elastically variable reservoir volume and is associated with a respective elastic resistance device to expansion of the respective reservoir volume.

[0059] In particular, a first elastic resistance device 21 for expansion of the respective water storage volume is associated with the first water storage chamber 20, and a second elastic resistance device 31 for expansion of the respective water storage volume, located opposite the first elastic resistance device 21, is associated with the second water storage chamber 30.

[0060] Advantageously, the first elastic resistance device 21 and the second elastic resistance device 31 have coincident main resistance directions lying on the same working axis K, but with opposing resistance directions. Preferably, the direction coincident with the working axis K is perpendicular to the rotation axis X of the impeller forming the pressure section 104 of the pump.

[0061] In fact, the expansion of the two chambers 20 and 30 (the respective directions of expansion indicated by the arrows hl and h2 in FIG. 3) are directed towards each other, and the resistance to these expansions is directed in opposite directions.

[0062] From a practical point of view, an increase in the pressure of the liquid in the tank corresponds to an expansion of the reservoir volume of both the first chamber 20 and the second chamber 30 against the resistance of the respective elastic resistance devices 21 and 31, and a decrease in the pressure of the liquid in the tank corresponds to a contraction of the reservoir volume.

[0063] Each elastic resistance device is independent or autonomous relative to the other elastic resistance devices and can only resist expansion of the volume of the chamber with which it is associated.

[0064] Advantageously, as will be explained below, the first resistance device 21 associated with the first water storage chamber 20 is at least partially disposed within the second resistance device 31 associated with the second water storage chamber 30.

[0065] For example, each module of the water storage tank 10 includes an outer casing 40 that defines, for example, an at least partially cylindrical central housing 41. Here, the first and second membranes 22 and 32 and the respective first and second closing lids 23 and 33 are fixed to opposite ends of the central housing 41. The central portions of the membranes are movable in the direction of the operating axis K. The spaces between the membranes 22 and 32 and the respective lids 23 and 33 define the first and second water storage chambers 20 and 30. The membranes are deformable and are formed, for example, from a rubber such as EPDM.

[0066] In practice, each water storage chamber 20 and 30 has a first chamber portion 20.1 and 30.1 with a fixed volume (the portion near the respective closing lid, which corresponds to the minimum volume that can be occupied by liquid or the state in which there is no expansion of the chamber due to liquid, as shown in Figure 4), and a second chamber portion 20.2 and 30.2 with a variable volume defined by the movement of the membrane (the maximum size is determined by the maximum amount of liquid that can be contained in the chamber or the maximum expansion of the chamber, as shown in Figure 3).

[0067] In these embodiments, each of the membranes 22 and 32 is connected along its edge in a liquid-tight manner between the respective closure lid 23 and 33 and the end of the outer casing 40 .

[0068] The first elastic resistance device 21 includes a first movable element 24 adapted to move from a first position corresponding to the minimum volume that can be occupied by the liquid in the first water storage chamber 20 (and corresponding to the fixed portion of the water storage chamber as shown in Figure 4) to a second position corresponding to the maximum volume that can be occupied by the liquid in the water storage chamber 20 (i.e., corresponding to the maximum volume of the second chamber portion having a variable volume as shown in Figure 3), and a first elastic resistor 25 adapted to generate elastic resistance to the movement of the movable element 24 from the first position to the second position.

[0069] The first movable element 24 comprises a fixing assembly 24.1 relative to the first membrane 22 and a first rod 24.2 integral with the first fixing assembly 24.1 and adapted to translate along a movement direction coinciding with the axis of action K (the axis of the rod coincides with the axis of action K). Movement of the first rod 24.2 causes movement of the first fixing assembly 24.1 and thus of a portion of the first membrane 22 in the movement direction, allowing a change in the volume of the first water storage chamber 20.

[0070] The first fixing assembly 24.1 comprises, for example, two discs fixed on a first rod 24.2. These discs block a portion 22.1 of the membrane 22 in a sandwich-like manner. The first disc is provided inside the chamber 20 and the second disc is provided outside the chamber 20. Naturally, the membrane can be most conveniently connected to the rod in different ways.

[0071] In practice, the first movable element 24 comprises a first membrane 22, which is fixed in a sealed state to a first lid of the first chamber (effectively the first chamber part), and to which is fixed a slider (two disks fixed to a first rod) adapted to interact with an elastic resistor 25, so that by moving a part of the membrane the volume of the chamber can be changed.

[0072] As mentioned above, the first elastic resistance device 21 includes a first rod 24.2, or a first fixing assembly 24.1, i.e. a first elastic resistor 25 adapted to generate elastic resistance to movement of the first membrane 22 from a first position to a second position.

[0073] In practice, the first movable element comprises a first membrane 22 connected in a sealed manner to the first chamber part, and sliders (two discs fixed to the first rod) are fixed to this membrane 22 and adapted to interact with elastic resistors 25 in order to allow the movement of a part of the membrane to vary the volume of the chamber.

[0074] Towards the end of the central housing 41 corresponding to the first chamber 20, the housing is closed by a divider 42 having a bowl portion 43 extending into the central housing 41 towards the second chamber 30. This bowl portion 43 is open towards the first chamber 20 and has a bottom 44. The length of this bowl portion is such that its bottom 44 preferably reaches an axially intermediate position of the central housing 41. The first elastic resistance device 21 is at least partly arranged in the space defined by the bowl portion 43.

[0075] In practice, the first elastic resistor 25 is disposed between the bottom 44 of the bowl portion 43 and the second disc of the first fixing assembly 24.1. The first rod 24.2 is adapted to translate at least partially within the bowl portion 43.

[0076] In this embodiment, the first elastic resistor 25 is a cylindrical helical spring, one end of which is placed on the bottom of the bowl portion 43 and which surrounds the first rod 24.2 (the rod is inserted into the cylindrical space of the spring), the axes of the spring and the rod preferably coinciding with each other and with the axis of action K.

[0077] It will be apparent that in other embodiments the first elastic resistor (and the second elastic body described below) may be formed by elements other than helical springs, for example elastic elements of different shapes, or elastomeric elements, or gas springs, etc.

[0078] Generally, for the purposes of this invention, the term "elastic" refers to a component that tends to deform when stressed in one direction and returns to its original shape when the stress is removed. Thus, the term elastic can refer to purely elastic, quasi-elastic, viscoelastic, non-linear elastic behavior, etc.

[0079] Preferably, the dividing body 42 forms a limit stop for the first movable element 24, for example defining an abutment (corresponding to the maximum volume of the first water storage chamber 20) for the second disc of the first fixed assembly 24.1.

[0080] As with the first elastic resistance device 21, the second elastic resistance device 31 includes a second movable element 34 adapted to move from a first position corresponding to the minimum volume that can be occupied by the liquid in the second water storage chamber 30 (and corresponding to the fixed portion of the water storage chamber as shown in Figure 4) to a second position corresponding to the maximum volume that can be occupied by the liquid in the second water storage chamber 30 (i.e., corresponding to the maximum volume of the second portion of the chamber having a variable volume as shown in Figure 3), and a second elastic resistor 35 adapted to provide elastic resistance to the movement of the second movable element 34 from the first position to the second position.

[0081] Similar to the first movable element, the second movable element 34 comprises a second fixing assembly 34.1 relative to the second membrane 32 and a second rod 34.2 integral with the second fixing assembly 34.1 (the rod and fixing assembly are not hatched for clarity of the drawing) and is adapted to translate along a movement direction coinciding with the axis of action K (the axis of the rod coincides with the axis of action K). Movement of the second rod 34.2 causes movement of the second fixing assembly 34.1 and thus of a portion of the second membrane 32 in the movement direction, allowing a volume change of the second water storage chamber 30.

[0082] Similar to the first assembly, the second fixing assembly 34.1 comprises, for example, two disks fixed on a second rod 34.2. These disks block a portion 32.1 of the membrane 32 in a sandwich-like fashion. The first disk is provided inside the second chamber 30, and the second disk is provided outside this chamber. Naturally, the membrane can be connected to the rod in different ways, depending on which is most convenient.

[0083] As mentioned above, the second elastic resistance device 31 includes a second rod 34.2, or a second fixing assembly 34.1, i.e. a second elastic resistor 35 adapted to generate elastic resistance to movement of the second membrane 32 from the first position to the second position.

[0084] In practice, the second movable element comprises a second membrane 32 connected to the first chamber part in a sealed state, and sliders (two discs fixed to a second rod) are fixed to this membrane 32 and adapted to interact with a second elastic resistor 35 in order to allow the movement of a part of the membrane to vary the volume of the chamber.

[0085] A second elastic resistor 35, for example a cylindrical helical spring, has one end resting against the divider 42 of the central housing 41 and surrounding the bowl portion 43, and its other end contacts the second disc of the second fixing assembly 34.1.

[0086] A portion of the bottom 44 of the bowl portion 43 facing the second chamber 30 serves as a limit stop for the second movable element 34. It should be noted that in this embodiment the movable element 34 includes a spacer bushing 34.3 fixed to the second disc of the second fixed assembly 34.1 and surrounding the second rod 34.2.

[0087] A guide system along the working axis K is associated with the first movable element 24 and the second movable element 34. For example, this guide system comprises a hole 45 passing through the bottom 44 of the bowl part 43 in a direction coaxial with the working axis K. The walls of this hole 45 guide, for example, the outside of the second rod 34.2 along the direction defined by the working axis K, so that the rod can enter the bowl part 43 in the space defined by the first spring 25.

[0088] In this embodiment, the second rod 34.2 is axially hollow and open at one end, thereby defining an axial channel 34.4 in which the first rod 24.2 is slidably disposed, guiding the first rod within the second rod.

[0089] It should be noted that in other embodiments, the first rod 24.2 may have a larger diameter than the second rod 34.2 and may be axially hollow to define a channel for sliding and guiding the second rod 34.2, which has a hole 45 that directly guides the first rod 24.2.

[0090] A damping element 46, such as a pair of opposed Belleville washers surrounding the second rod 24.2, may be provided in a portion of the bottom 44 of the bowl portion 43 that acts as a limit stop for the second movable element 34. This may be effective in eliminating water hammer.

[0091] The elastic resistors 25 and 35 are arranged outside the respective water storage chambers they act on, between the movable elements 24 and 34 and the respective abutment stops 42 and 44, and are configured to compress in the direction from the respective movable elements to the abutment stops.

[0092] It should be noted that the first elastic resistor 25 of the first elastic resistance device 21 associated with the first water storage chamber 20 is primarily positioned within the space of the second elastic resistor 35 of the second elastic resistance device 31 associated with the second water storage chamber 30.

[0093] It should also be noted that the movable elements 24 and 34 can be integral with or form the respective portions of the walls of the respective water storage chambers 20 and 30, and movement of at least a portion of the respective movable elements 24 and 34 allows the volume of the water storage chambers to expand.

[0094] Each of the chambers 20 and 30 has at least one passage 27 and 37 for liquid to enter the chamber and preferably for liquid to exit the chamber. Preferably, the passage is provided in the closure lid 23 and 33.

[0095] These passages 27 and 37 are operatively connected via respective ducts 47 to the pump space 109, where the liquid is at substantially the same pressure as the outlet 103, or the delivery pressure of the pump.

[0096] In a preferred embodiment, the water storage chambers in water storage tank 10 are substantially the same or all have the same (minimum and maximum) volume. Therefore, what causes the expansion of chambers 20 and 30 to differ is the different stiffness values ​​of elastic resistors 25 and 35.

[0097] It should be noted that in other embodiments, the stiffness of the two springs may be the same and the expansion of the two chambers, i.e., the volume change therein, may be the same (as if there were actually a single expansion chamber divided into two sub-chambers opposite each other).

[0098] In one module, for a given pressure value in the reservoir chambers 20 and 30, a first volume change in the first reservoir chamber 20 is associated with a first elastic resistance device, and a second volume change in the second reservoir chamber 20, different from the first change, is associated with a second elastic resistance device (the first and second elastic resistance devices are configured to allow different reservoir volumes for the two reservoir chambers). Generally, in multiple modules, the elastic resistance devices are preferably configured to allow different reservoir volumes in all reservoir chambers for a given pressure value of the liquid.

[0099] Pump 100 further includes an electronic control device 140 (e.g., disposed within housing 140A) to which electric motor 108 of impeller 105 is operatively connected, and a pressure gauge 141, preferably a pressure switch, adapted to measure the pressure in the region between outlet 103 and the pressurization section outlet. The pressure gauge is adapted to measure the pressure in the pump's delivery section downstream of the impeller (alternatively, the pressure gauge may be disposed downstream of outlet 103). Electric motor 108 is thereby adapted to rotate the impeller when a first pressure value measured by pressure switch 141 is reached, and to interrupt operation of the impeller when a second pressure value measured by the pressure switch, which is greater than the first pressure value, is reached.

[0100] As the pump operates and the liquid pressure on the pump delivery increases, this pressure increase also occurs in the reservoir chambers 20 and 30 (which are all at the same pressure), which begin to fill more in the second chamber portions 22.2 and 32.2, deforming the membranes 22 and 32 (expanding the chamber volume) and resisting the elastic resistance of the compressed springs 23 and 33. Meanwhile, a decrease in the liquid pressure on the delivery side of the pump, or in the reservoir chambers 20 and 30, corresponds to a contraction of the reservoir volume previously subjected to expansion in the chambers 20 and 30, or a return of the membranes 22 and 23, urged by the springs 23 and 33, towards the first chamber portions 20.1 and 30.1.

[0101] 5 shows the case of two modules, where there are four chambers, including two first chambers 20 and two second chambers 30. In some embodiments where multiple modules M are arranged side by side, the closure lids 22 and 23 may be common to adjacent first chambers and adjacent second chambers, respectively.

[0102] Advantageously, the four elastic resistors / springs associated with the four chambers all have different elastic stiffnesses. For example, the first elastic resistor has an elastic stiffness K1, the second elastic resistor has an elastic stiffness K2, where K2>K1, the third elastic resistor has an elastic stiffness K3, where K3>K2, and the fourth elastic resistor has an elastic stiffness K4, where K4>K3.

[0103] The reservoir chambers are substantially identical to one another, and in particular, the membranes 23 and 33 all have the same surface. Therefore, when the pressure in the reservoir chambers 20 and 30 increases to the same value (which is always the same pressure in all), their volumetric expansion is differentiated based on the stiffness of the springs 23 and 33. More specifically, the expansion in the chambers increases as a function of the stiffness associated with the relative membrane movement (the stiffer the spring of the elastic resistance device, the smaller the movement of the movable element associated with the membrane or the smaller the volume change, i.e., expansion, of the chamber). The four inflatable reservoir chambers of the same arrangement have associated four springs of different stiffnesses that resist the expansion of the chambers. This is described, for example, in European Patent Application No. 4015826. The same explanation of general operation is incorporated herein.

[0104] The fact that it has reservoir chambers that expand in different ways allows the pump to be used in many different operating situations. In fact, each reservoir chamber has its own resistance to expansion with its own stiffness, which allows the pump to operate in a given pressure range. In fact, the pump contains a reservoir tank (chamber) that is already adjusted (during the assembly or design of the pump). Therefore, it is sufficient to place the pump in a system without adjusting any element of the tank.

[0105] In practice, the first chamber can expand, for example, up to a value Pa, at which the movable element of the first elastic resistance device reaches its limit stopper (the membrane expands the chamber to the maximum and the first spring is compressed by a value Wl). The second chamber can expand, for example, up to a value Pb > Pa, at which the movable element of the second elastic resistance device reaches its limit stopper (the membrane expands the second chamber to the maximum and the second spring is compressed by a value Wb < Wa). The third chamber can expand, for example, up to a value Pc > Pb, at which the movable element of the third elastic resistance device reaches its limit stopper (the membrane expands the third chamber to the maximum and the third spring is compressed by a value Wc < Wb). The fourth chamber can expand, for example, up to a value Pd > Pc, at which the movable element of the fourth elastic resistance device reaches its limit stopper (the membrane expands the fourth chamber to the maximum and the fourth spring is compressed by a value Wd < Wc).

[0106] The graph of FIG. 8 shows a total head / flow rate graph showing the operating curve n of the pump. In this graph, four operating ranges Po - Pa - Pb - Pc - Pd of the pump are highlighted (the limits of each range coincide with the lower and upper limits of the operating pressure of the tank in that range). These ranges are related to the stiffness of the springs of the four resistance devices, that is, the differences in the expansion of the four water storage chambers.

[0107] For example, when it is necessary to operate the pump in the pressure range between atmospheric pressure Po (for example, when the pump pumps water from an unpressurized water tank) and the total head value Pa of about 22 meters (corresponding to a pressure increase of about 2.2 bar), when the pump is connected to a closed system, the pump operates and the system and the water storage chamber are pressurized up to pressure Pa. At this time, all four chambers are filled with liquid and expand according to their respective expansion capabilities. That is, the first water storage chamber expands more than the second chamber, the second chamber expands more than the third chamber, and the third chamber expands more than the fourth chamber.

[0108] The pressure drop on the delivery side of the pump causes a contraction of the volume in the water storage chamber. When the pressure drops below the required threshold value, the pump pressurizes the tank again and supplies new water to the water storage chamber until the operating pressure Pa of the tank is reached.

[0109] For example, in a system having an operating range between the total head values Pb = 35 m and Pc = 52 m (about 3.5 bar and 5.2 bar), when the same pump as in the above-described embodiment is installed, it can be seen how unnecessary the adjustment of the water storage tank is. In fact, when the pump fills all the chambers 20 with water up to the pressure Pb, when the first value Pa is reached, the first water storage chamber is fully inflated. As the pressure continues to rise and reaches Pb, the second water storage chamber is fully inflated. As the pressure rises again and reaches Pc, that is, the maximum operating pressure, the third water storage chamber is substantially fully inflated (it may not be fully inflated depending on the spring configuration). When this pressure is reached, the pump stops operating. In the fourth water storage chamber, the membrane expands by a fraction of its allowable volume, or the spring associated with it is compressed by a value Wd’ < Wd.

[0110] It should be noted that the remaining expansibility of the fourth chamber can be used to counteract any pressure peaks caused by water hammer (of course, the fourth spring needs to be sized from the perspective of rigidity so that it can absorb these peaks).

[0111] Also, similar to the case where the rigidity of the elastic resistance elements associated with the chambers is different, the concept of the difference in expansion ability can also be utilized in a system having the same rigidity. In this case, it should be noted that the size of the membrane in the chamber (from the perspective of surface area) is different. In fact, under the same pressure conditions, increasing the area of the membrane increases the elastic resistance force. Therefore, two chambers having different membrane sizes and elastic resistance springs having the same rigidity have different amounts of change in the expansion volume.

[0112] Compared to the case described in EP 4015826, the solution according to the invention provides a particularly compact tank. By using two elastic resistance devices arranged opposite each other with opposite main directions of resistance to expansion, the expansion chambers can be arranged axially in front of each other and, if necessary, part of the actuating structure of one chamber can be arranged inside the actuating structure of the other chamber, optimizing space. In particular, when the springs are arranged one inside the other, the overall dimensions are very compact.

[0113] Being very compact, a tank constructed in this way can be used with a variety of pumps.

[0114] As mentioned above, Figures 6 and 7 show a second embodiment of a tank module generally designated by reference numeral 110. In this case, the water reservoir 110 includes a single water reservoir chamber A formed by a first portion of a water reservoir chamber 120 and a second portion of a water reservoir chamber 130. Each portion of the water reservoir chambers 120 and 130 defines a respective elastically variable water reservoir volume and is associated with a respective elastic resistance device to expansion of the respective water reservoir volume.

[0115] In particular, a first elastic resistance device 121 against expansion of the respective water storage volume is associated with a first portion of the water storage chamber 120, and a second elastic resistance device 131 against expansion of the respective water storage volume, located opposite the first resistance device 121, is associated with a second portion of the water storage chamber 130.

[0116] Advantageously, the first elastic resistance device 121 and the second elastic resistance device 131 have, as in the above-described embodiment, coincident main directions of resistance located on the same axis of action K, but with opposite directions of resistance.

[0117] In fact, the expansion of the two chambers 20 and 30 (the directions of expansion indicated by the arrows h1' and h2' in Figure 7) are opposite to each other, and the directions of resistance to these expansions are directed towards each other.

[0118] From a practical standpoint, an increase in the pressure of the liquid in the tank corresponds to an expansion of the reservoir volume in both the first and second portions of the chambers 120 and 130 against the resistance of the respective elastic resistance devices 121 and 131, and a decrease in the pressure of the liquid in the tank corresponds to a contraction of the reservoir volume.

[0119] Each elastic resistance device may be independent or autonomous relative to the other elastic resistance devices, and may only resist expansion of the volume of the portion of the chamber with which it is associated.

[0120] For example, each module of the water storage tank 110 includes an outer casing 140 that defines, for example, an at least partially cylindrical central housing 141. Here, the first and second membranes 122 and 132 and the respective first and second closure domes 123 and 133 are fixed to opposite ends of the central housing 141. The central portions of the membranes are movable in the direction of the operating axis K, as will be described below. The spaces between the membranes 122 and 132 and the centerline plane W of the central housing 141 define first and second portions of the water storage chambers 120 and 130. The membranes are deformable and, as in the previously described embodiments, are formed from rubber, for example, EPDM.

[0121] In practice, each portion of the water storage chambers 120 and 130 has a first chamber portion 120.1 and 130.1 with a fixed volume (the portion located near the respective closure dome and corresponding to the minimum volume that can be occupied by the liquid or the state in which there is no expansion of the chamber portion due to the liquid, as shown in Figure 6), and a second chamber portion 120.2 and 130.2 with a variable volume defined by the movement of the membrane (the maximum size of which is determined by the maximum amount of liquid that can be accommodated in the chamber portion or the maximum expansion of the chamber portion, as shown in Figure 7).

[0122] In these embodiments, each of the membranes 122 and 132 is connected along its edge in a liquid-tight manner between the respective closure dome 123 and 133 and the end of the casing 140 or the end of the central housing 141 .

[0123] The first elastic resistance device 121 includes a first movable element 124 adapted to move from a first position corresponding to the minimum volume that can be occupied by a liquid in the first portion of the water storage chamber 120 (and corresponding to the fixed portion of the water storage chamber portion as shown in FIG. 6) to a second position corresponding to the maximum volume that can be occupied by a body in the portion of the water storage chamber 120 (i.e., corresponding to the maximum volume of the second portion of the chamber portion having a variable volume as shown in FIG. 7), and a first elastic resistor 125 adapted to provide elastic resistance to the movement of the movable element 124 from the first position to the second position.

[0124] The first mobile element 124 has a fixed assembly 124.1 relative to the first membrane 122 and comprises two disks blocking a portion 122.1 of the membrane 122, for example in a sandwich-like manner: the first disk is provided inside the first portion of the chamber 120, the second disk is provided outside this portion of the chamber 120. Naturally, the membrane can be most conveniently connected to the rod in different ways.

[0125] The first rod 124.2 is integral with a first fixing assembly 124.1, for example a first disk, and is adapted to translate along a movement direction (the axis of the rod coincides with the axis of action K) that coincides with the axis of action K. Movement of the first rod 124.2 corresponds to movement of the first fixing assembly 124.1 (and vice versa), which in turn causes movement of a portion of the first membrane 122 in the movement direction, allowing a volume change of the first portion of the water storage chamber 120.

[0126] In practice, the first movable element 124 comprises a first membrane 122, which is connected in a sealed manner to a first closure dome of a first part of the chamber (in practice, a first part of the chamber part), and to this membrane 122 is fixed a slider (two disks fixed to a second rod) adapted to interact with an elastic resistor 125, so that by moving a part of the membrane the volume of the part of the chamber can be changed.

[0127] In practice, the first elastic resistor 125 is arranged between the bottom 123.1 of the dome 123, which forms the abutment stop for the first elastic resistor 125, and an abutment on the second disk of the first fixing assembly 124.1. Preferably, a sleeve 123.2 is surrounded by the elastic resistor 125 and extends from the bottom 123.1.

[0128] In this embodiment, the first elastic resistor 25 is a cylindrical helical spring having one end resting on the bottom of the dome 123 and surrounding a sleeve 123.2 extending from the bottom 123.1 of the dome 123.

[0129] It will be apparent that in other embodiments the first elastic resistor (and the second elastic body described below) may be formed by elements other than helical springs, for example elastic elements of different shapes, or elastomeric elements, or gas springs, etc.

[0130] Generally, for the purposes of this invention, the term "elastic" refers to a component that tends to deform when stressed in one direction and returns to its original shape when the stress is removed. Thus, the term elastic can refer to purely elastic, quasi-elastic, viscoelastic, non-linear elastic behavior, etc.

[0131] As with the first elastic resistance device 121, the second elastic resistance device 131 includes a second movable element 134 adapted to move from a first position corresponding to the minimum volume that can be occupied by the liquid in the second portion of the water storage chamber 130 (and corresponding to a fixed portion of a portion of the water storage chamber as shown in Figure 6) to a second position corresponding to the maximum volume that can be occupied by the liquid in the second portion of the water storage chamber 130 (i.e., corresponding to the maximum volume of the second portion of the chamber portion having a variable volume as shown in Figure 7), and a second elastic resistor 135 adapted to provide elastic resistance to the movement of the second movable element 134 from the first position to the second position.

[0132] The second movable element 134 has a second fixing assembly 134.1 relative to the first membrane 132 and comprises two disks blocking a portion 132.1 of the membrane 132, for example in a sandwich-like manner, the first disk being arranged inside the second portion of the chamber 130 and the second disk being arranged outside this portion of the chamber 130. Naturally, the membrane can be most conveniently connected to the rod in different ways.

[0133] The second rod 134.2 is integral with a first fixing assembly 134.1, for example a first disk, and is adapted to translate along a movement direction (the axis of the rod coincides with the axis of action K) that coincides with the axis of action K. Movement of the second rod 134.2 corresponds to movement of the second fixing assembly 134.1 (and vice versa), which in turn causes movement of a portion of the second membrane 132 in the movement direction, allowing a volume change of the second portion of the water storage chamber 130.

[0134] As mentioned above, the second elastic resistance device 131 includes the second rod 134.2, or the second fixing assembly 134.1, i.e. the second elastic resistor 135 adapted to generate elastic resistance to the movement of the second membrane 132 from the first position to the second position.

[0135] In practice, the second movable element comprises a second membrane 132, which is connected to the first chamber part 130 in a sealed state. Also fixed to the second membrane 132 is a slider (two disks fixed to a second rod) adapted to interact with a second elastic resistor 135. This allows the volume of a part of the chamber to be changed by moving a part of the membrane.

[0136] The second elastic resistor 135 is a cylindrical helical spring mounted so that one end abuts against the bottom 133.1 of the second dome 133 to form an abutment stop for the spring 135 and the other end abuts against an abutment on the second disc of the second fixing assembly 134.1.

[0137] A sleeve 133.2 surrounded by a spring 135 extends from the bottom 133.1 of the second dome 133.

[0138] A guide system 144 along the working axis K is associated with the first movable element 124 and the second movable element 134. For example, this guide system includes a duct 145 coaxial with the working axis K. The duct 145 is formed in the second rod 134.2 and opens towards the first rod 124.2, the first rod 124.2 sliding in the duct 145 during at least part of its movement. A bushing 146 is slidably coupled at one end to the outer surface of the second rod 134.2 and at the other end to the outer surface of the first rod 124.2, so that the two parts of the chamber form a guide element at maximum expansion, as shown in FIG. 7 .

[0139] It should be noted that in other embodiments the guide system may be formed by a first rod and a second rod housed outside a portion of the chamber, for example in the respective domes 123 and 133, and guided within the sleeves 123.2 and 133.2.

[0140] Also, note that in other embodiments, there may not be a guide system with a moving disc as a result of the shape of membranes 22 and 122 .

[0141] The single chamber A formed by the first and second portions 20 of the chambers 120 and 130 has at least one passage 127 for liquid to enter and / or exit the chamber. Preferably, the passage 127 is provided on the side of the casing 140 at the same height as the plane W.

[0142] This passage 127 is operatively connected via a respective duct 147 to the pump space 109, where the liquid is at substantially the same pressure as the outlet 103, i.e. the delivery pressure of the pump.

[0143] Also, in this embodiment, as with the embodiment shown in Figures 2-5, the portions of the water storage chamber within the water storage tank 10 are substantially the same or all have the same (minimum and maximum) volume. Therefore, it is the different stiffness values ​​of the elastic resistors 125 and 135 that cause the expansion of the respective portions of the chambers 120 and 130 to differ.

[0144] It should be noted that in other embodiments, the stiffness of the two springs may be the same and the expansion of the two parts of the chamber, i.e. the volume change therein, may be the same.

[0145] In one module, for a given pressure value in the portions of the reservoir chambers 120 and 130, a first volume change in a first portion of the reservoir chamber 20 is associated with a first elastic resistance device, and a second volume change in a second portion of the reservoir chamber 20, different from the first change, is associated with a second elastic resistance device (the first and second elastic resistance devices are configured to allow different reservoir volumes for the two portions of the reservoir chamber). Generally, in multiple modules, the elastic resistance devices are preferably configured to allow different reservoir volumes in all portions of the reservoir chamber for a given pressure value of the liquid.

[0146] In effect, the liquid in the single reservoir chamber A formed by the portions of chambers 120 and 130 expands or contracts the volume of chamber A, which acts differently on the two membranes 122 and 123, as a function of the stiffness of the elastic resistance elements associated with each membrane. If a partition is placed along W to physically divide chamber A into two sub-chambers (which in fact correspond to the portions of chambers 120 and 130), each with its own access, this would give a solution equivalent to that described in the first example of this specification (although of course the arrangement of the elastic resistance elements or springs would be different), or from a practical point of view would correspond to the case of two tanks placed opposite each other and with the axes of action of the elastic resistance elements coaxial with each other, as described in European Patent Application No. 4015826.

[0147] In this embodiment and in the embodiment described above, the distribution of space around the central axis of the two water storage chambers allows such a tank to be used in a submersible pump where the size of the pump casing has a predominantly axial dimension.

[0148] For example, Figure 9 shows a perspective view of a submersible pump, in which an impeller assembly 1005, a motor 1008, and a tank according to the invention are arranged along a main axis within an outer casing 1001 that is largely axially expanded. In Figure 9, the tank is of the first embodiment (i.e., the one associated with Figures 2 to 5), but the tank of the second embodiment, or a tank according to the invention having an embodiment further different from that described in detail above, can also be used. In practice, in this application, the tank is arranged within the casing, as in the above-described embodiments, and not at its outer edge, but with particularly limited overall dimensions.

[0149] It should be noted that the above description merely represents possible non-limiting embodiments of the present invention, and that changes in form and arrangement may be made without departing from the concept on which the invention is based. Any reference signs in the accompanying claims are provided purely to facilitate the reading of the claims in light of the above description and the accompanying drawings, and do not limit the scope of protection in any way.

Claims

1. A water storage tank including at least one first portion and at least one second portion of a water storage chamber, the reservoir chamber is adapted to contain a liquid, the liquid contained in the first and second portions of the reservoir chamber being under the same pressure, and the first and second portions each defining an elastically variable reservoir volume; a first elastic resistance device is associated with the first portion of the water storage chamber for resisting expansion of the corresponding water storage volume, and a second elastic resistance device is associated with the second water storage chamber for resisting expansion of the corresponding water storage volume, whereby an increase in pressure of the liquid in the water storage tank corresponds to an expansion of the water storage volume against the resistance of the corresponding elastic resistance device, and a decrease in pressure of the liquid in the water storage tank corresponds to a contraction of the water storage volume, each of the elastic resistance devices having a main direction of resistance to expansion, and the two elastic resistance devices are arranged opposite each other, whereby the main directions of resistance to expansion are opposite to each other; Water tank.

2. 2. The water tank according to claim 1, wherein the main directions of resistance to expansion of the oppositely disposed elastic resistance devices are substantially aligned on a single axis of action in opposite directions.

3. Each of the elastic resistance devices comprises: a movable element adapted to move at least partially from a first position corresponding to a minimum volume that can be occupied by the liquid in the reservoir chamber to a second position corresponding to a maximum volume that can be occupied by the liquid in the reservoir chamber; a resilient resistor adapted to provide a resilient resistance to movement of said movable element from said first position to said second position; Including, Preferably, the elastic resistor is disposed between the movable element and the abutment stopper outside the first and second portions of the water storage chamber, and is configured to compress in a direction from the movable element to the abutment stopper.

3. The water storage tank according to claim 1 or 2.

4. 4. The water tank of claim 3, wherein at least one of the movable elements is integral with or forms a wall portion of one of the first and second portions of the water storage chamber, and movement of at least a part of the movable element allows the volume of the first or second portion of the water storage chamber to expand, and preferably the direction of movement of at least a part of the movable element coincides with the main direction of resistance to expansion of the corresponding first or second portion of the water storage chamber.

5. 5. The water storage tank of claim 3, wherein each of the first and second portions of the water storage chamber has a first chamber portion with a fixed volume and a second chamber portion with a variable volume defined by movement of the movable element of the respective elastic resistance device.

6. 6. The water tank of claim 5, wherein the movable element comprises a membrane connected to the first chamber portion in a sealing manner, preferably with a slider fixed to the membrane, the slider adapted to interact with the elastic resistor to allow movement of a portion of the membrane to vary the volume of the water storage chamber.

7. 7. The water storage tank according to claim 1, wherein, for a given pressure value in the first and second portions of the water storage chamber, at least one first elastic resistance device is associated with a first volume change in the corresponding at least one first portion of the water storage chamber, and at least one second elastic resistance device is associated with a second volume change in the corresponding at least one second portion of the water storage chamber, the first volume change and the second volume change being different from each other, i.e., the at least one first elastic resistance device and the at least one second elastic resistance device are configured to allow different expansion volumes in the at least one first portion and at least one second portion of the water storage chamber, respectively, and preferably, for a given pressure value, the first elastic resistance device and the second elastic resistance device are configured to allow different expansion volumes in all of the first and second portions of the water storage chamber.

8. The water tank according to any one of claims 1 to 7, wherein the at least two first elastic resistance devices and the at least two second elastic resistance devices have different elastic stiffnesses from each other.

9. 9. The water tank of claim 1, wherein the first and second portions of the water storage chamber all have the same minimum and maximum volumes that the liquid can occupy.

10. 10. The water storage tank of claim 1, wherein at least two of the portions of the water storage chamber, preferably all of the portions of the water storage chamber, have a first chamber portion with a fixed volume and a second chamber portion with a variable volume defined by the movement of the movable element, wherein the fixed volume of the first chamber portion is the same for at least two of the portions of the water storage chamber, and wherein the at least two portions of the water storage chamber are associated with elastic resistors with different stiffnesses so as to enable different expansions in the portions of the water storage chamber, whereby when the pressure of the liquid in the at least two portions of the water storage chamber is the same, the portions of the water storage chamber can have different volumes.

11. The water tank of any one of claims 1 to 10, wherein the first and second portions of the water storage chamber form a single water storage chamber.

12. 12. The water tank of claim 11, wherein the single water storage chamber includes a central casing that at least partially defines the first and second portions of the single water storage chamber, and the central casing has two open sides on either side that are closed by two opposing domes having recesses in which each of the elastic resistors is housed.

13. 13. The water tank of claim 12, wherein an edge of the membrane is sealingly secured to an open end edge of the dome.

14. 11. The water tank of claim 1, comprising at least one first water storage chamber formed by at least one first portion of the water storage chamber, and at least one second water storage chamber formed by at least one second portion of the water storage chamber.

15. 15. The water tank of claim 14, wherein the first elastic resistance device associated with the first water storage chamber is at least partially disposed within the second elastic resistance device associated with the second water storage chamber.

16. 16. The water tank of claim 15, wherein the elastic resistor of the first elastic resistance device associated with the first water storage chamber is primarily located within the space occupied by the elastic resistor of the second elastic resistance device associated with the second water storage chamber, and preferably the elastic resistor is an axial spring, preferably a helical spring, also preferably a cylindrical spring.

17. 17. A water tank as claimed in claim 15 or 16, wherein the movable element of the first elastic resistance device is adapted to slide within an axial channel defined in the movable element of the second elastic resistance device, or vice versa, the movable element of the second elastic resistance device is adapted to slide within an axial channel defined in the movable element of the first elastic resistance device.

18. 18. The water tank of claim 1, comprising an outer casing defining a central housing, with closing lids fixed to opposite end portions of the central housing, whereby the first water storage chamber and the second water storage chamber are defined at the closed ends, and the first elastic resistance device and the second elastic resistance device are disposed within the central housing and adapted to provide resistance in opposite directions to each other.

19. 20. The water tank of claim 18, wherein for each of the chambers, the respective lid defines a portion of the first chamber portion, at least one passage is defined on the lid for entry / exit of the liquid, and the passages of the first chamber and the second chamber are under the same pressure.

20. 20. The water tank according to claim 18 or 19, comprising a modular structure provided with at least one module, each of said modules comprising one central housing having two said water storage chambers on either side thereof, and when there are at least two said modules, the central housings of said modules respectively have central axes arranged parallel and side by side to each other, and preferably the adjacent water storage chambers of two adjacent said modules comprise the same said lid.

21. 21. The water tank of claim 1, wherein, for a given pressure value in the water storage chambers, at least one first elastic resistance device is associated with a first volume change in at least one corresponding first water storage chamber, and at least one second elastic resistance device is associated with a second volume change in at least one corresponding second water storage chamber, the first volume change and the second volume change being different from each other, i.e., the at least one first elastic resistance device and the at least one second elastic resistance device are configured to allow different expansion volumes in the at least one first water storage chamber and the at least one second water storage chamber, respectively, and preferably, for a given pressure value, the first elastic resistance device and the second elastic resistance device are configured to allow different expansion volumes in all the water storage chambers.

22. The water tank according to any one of claims 1 to 21, wherein the at least two first elastic resistance devices and the at least two second elastic resistance devices have different elastic stiffnesses from each other.

23. A water tank according to any one of the preceding claims, wherein the part of the water storage chamber, or all the complete water storage chamber, has the same minimum and maximum volume that the liquid can occupy.

24. 24. A water tank as claimed in any one of claims 1 to 23, wherein at least two of the water storage chambers, preferably all of the water storage chambers, have a first chamber portion with a fixed volume and a second chamber portion with a variable volume defined by movement of the movable element, the fixed volume of the first chamber portion being the same for at least two of the water storage chambers, and at least two of the water storage chambers are associated with the elastic resistors having different stiffnesses, which allows the expansion of the water storage chambers to be different, so that when the pressure of the liquid in the at least two water storage chambers is the same, the water storage chambers can have different volumes.

25. 1. A hydraulic pump, comprising: a path for liquid from at least one suction port for the liquid within the hydraulic pump to a delivery port for the liquid from the hydraulic pump, the path including: a pressure section downstream of said suction inlet configured to increase the pressure of said liquid; a reservoir for pressurized liquid according to any one of claims 1 to 24 downstream of the pressurization section; wherein the at least one first portion and the at least one second portion of the reservoir chamber are all under the same liquid delivery pressure. Hydraulic pump.

26. an outer casing, the passage for the liquid being defined within the outer casing, a compartment for accommodating at least one impeller of said hydraulic pump; a space for said liquid under the delivery pressure of said hydraulic pump, on one side of said compartment, so as to develop substantially following the development of the axis of rotation of said at least one impeller; wherein the first and second portions of the water storage chamber of the water storage tank are in direct communication with the space, preferably the direction of action of the elastic resistance device is perpendicular to the axis of the motor of the hydraulic pump, preferably a base plate for the hydraulic pump is provided on the opposite side of the compartment, whereby the space is located above the compartment, and preferably the delivery outlet for the liquid is provided in the space.

26. The hydraulic pump of claim 25.

27. 26. The hydraulic pump of claim 25, wherein the hydraulic pump is an axially deploying submersible pump, and the at least one water reservoir is disposed within a casing of the submersible pump and has an action axis of a resilient resistance device that deploys parallel to an axial deployment axis of the submersible pump.

28. 26. The hydraulic pump of claim 25, further comprising: an electronic control unit operatively connected to an electric motor that drives a pressure member of the pressurizing section of the hydraulic pump; and a pressure gauge that is a pressure switch adapted to measure the pressure in a region between the liquid delivery section and a delivery outlet, whereby the electric motor is adapted to operate the pressure member when a first pressure value measured by the pressure gauge is reached, and to interrupt operation of the pressure member when a second pressure value measured by the pressure gauge is reached, the second pressure value being greater than the first pressure value.

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