WO2003074873A1

WO2003074873A1 - Apparatus for on/off controlling a pump in a liquid distribution network

Info

Publication number: WO2003074873A1
Application number: PCT/IT2002/000133
Authority: WO
Inventors: Carlo Mensi; Ettore Verdini
Original assignee: Watertech, S.P.A.
Priority date: 2002-03-04
Filing date: 2002-03-04
Publication date: 2003-09-12
Also published as: AU2002247957A1

Abstract

Apparatus (1) for controlling the starting and stopping of a pump in a liquid-supply network comprises a first chamber (14), a pressure switch (102) for sending a signal to the pump in the presence of a predetermined minimum value of the pressure in the first chamber (14), a flow switch (46) for sending a signal to the pump in the presence of a minimum flow of liquid towards the supply network, and a second chamber (16) provided with an opening (18) towards the first chamber (14). The apparatus further comprises a closure member (74) which shuts off the opening (18), forming a seal between the first chamber (14) and the second chamber (16). The apparatus can stabilize the apparent pressure head supplied by the pump ot the user, permitting prompt restarting of the pump.

Description

DESCRIPTION "Apparatus for on/off controlling a pump in a liquid distribution network"

The present invention relates to apparatus for controlling the starting and stopping of a pump in a network for the supply of a liquid, particularly of water, for applications in domestic and/or industrial environments .

During the installation of water-supply systems, it is usual to provide a pump and apparatus downstream of the pump for controlling the starting and stopping of the pump.

For example, it is known to use, between the pump and the user, apparatus which includes a chamber for holding the liquid, a device which detects a flow of water towards the user (a flow switch) and which can send a signal relating to the passage of a predetermined flow-rate of liquid, and a device which detects the pressure of the water in the holding chamber (a pressure switch) and which can send a signal when a predetermined pressure of the liquid- in the holding chamber is reached.

The apparatus controls the starting and/or the stopping of the pump in accordance with the various operating conditions, on the basis of the signals sent by the flow switch and/or by the pressure switch.

An example of apparatus as referred to . above is described in the Applicant's European patent No. 539721. Apparatus of the type described above has the disadvantage that it supplies, to the supply network disposed downstream, a liquid the pressure of which is related to the operative conditions of the pump associated therewith.

In other words, the conditions of the system supplying the pump may vary, for example, for seasonal reasons (lowering or raising of the liquid level in wells or in reservoirs) or owing to variations in the condition of the supply mains due, for example, to the connection of the system to new users. These conditions lead to an undesired variability of the apparent pressure head of the pump towards the user. ,

On the basis of the conditions which have arisen, the pressure head from which the user benefits may be too low, with consequent inconvenience to users, or too high, with the possibility of causing damage to the devices connected to the supply network or malfunctions of the control apparatus.

There is therefore a need to provide apparatus for controlling the starting and stopping of a pump which can stabilize the apparent pressure head supplied by the pump to the user, permitting prompt restarting.

The problem underlying the present invention is that of devising apparatus for controlling the starting and stopping of a pump of a liquid-supply network which has structural and functional characteristics such as to satisfy the above-mentioned needs and at the same time to overcome the disadvantages discussed with reference to the prior art .

This problem is solved by control apparatus according to Claim 1. Further embodiments of the apparatus according to the invention are described in the dependent claims .

Further characteristics and the advantages of the control apparatus according to the present invention will become clear from the following description of a preferred but non-limiting embodiment thereof, in which:

Figure 1 shows, in section, apparatus for controlling the starting and stopping of a pump, in a condition in which the pump is stopped and the network is under pressure,

Figure 2 shows, in section, the apparatus of Figure 1 in a condition in which liquid is supplied to the network,

Figure 3 shows, in section, the apparatus of Figure 1 in a lockout condition owing to an absence of flow and pressure,

Figure 4 is a partially-sectioned, perspective view of the apparatus of Figure 3 , and

Figure 5 shows a schematic diagram of the head of a pump, the head at the user of a supply network, the head at the user of a supply network associated to the apparatus of Figure 1, in a first regulation configuration, and the head at the user of a supply network associated to the apparatus of Figure 1, in a second regulation configuration.

With reference to the appended drawings, control apparatus according to the invention is generally indicated 1.

The apparatus 1 comprises an outer casing 2 which extends, with substantial cylindrical symmetry, about a horizontal axis X-X. The casing can be operatively associated with the supply network by means of an outlet duct 4 and to the pump by means of an inlet duct 6.

A cylindrical body 8 and a shank 10, which are hollow and are fixed together by mechanical connection means 12 such as screws, bolts, or the like, can be recognized in the casing 2.

The cylindrical body 8 comprises a first chamber 14 which is in communication with the outlet duct 4 of the casing 2 and a second chamber 16 which is in communication with the inlet duct 6 of the casing. The first chamber 14 and the second chamber 16 are in communication with one another through an opening 18.

For the control apparatus 1, the first chamber 14 forms a low-pressure chamber and the second chamber forms a high-pressure chamber since, in normal operative conditions, the low-pressure chamber is intended to contain the liquid at a pressure lower than the pressure of the liquid contained in the high-pressure chamber. However, it is intended that, for particular operative conditions generally connected with transient operating states of the apparatus, the low-pressure chamber may contain liquid at a pressure equal to the pressure of the liquid contained in the high-pressure chamber.

In a preferred embodiment, the casing 2 has internal partitions 20 which are fixed, in the region of respective end portions 20', to a sealing plate 22, so that the partitions and the plate define the low- pressure chamber 14 and the high-pressure chamber 16, inside the cylindrical body 8.

The sealing plate 22 has a through-cavity which forms the opening 18 between the high-pressure chamber 16 and the low-pressure chamber 14. The diameter of the opening 18 of the plate 22 is preferably calibrated in order to give rise to a controlled drop in pressure for the liquid which passes through the opening 18 from the second chamber 16 to the first chamber 14. In a preferred embodiment of the apparatus 1, in which the reference diameter of the inlet duct 6 or of the outlet duct 4 is between 20mm and 38mm and preferably equal to 31.75mm (corresponding to 1 "), the diameter of the opening 18 is between 24mm and 15mm, preferably between 21mm and 18mm and, advantageously, is equal to 19.5mm. Laboratory tests have also shown satisfactory results for diameters of the opening 18 of between 20mm and 22mm.

In laboratory tests, these dimensions have shown unusual pressure-reducing effects which have the capability not to alter the operation of the further devices of the apparatus and, in particular, the operation of a flow switch described in detail below.

The sealing plate 22, which is fixed firmly to the partitions 20, is substantially cylindrical and extends about the horizontal axis X-X of the cylindrical body 8.

In its portion facing the high-pressure chamber 16, the plate has an annular cavity 24 so that the sealing plate 22 faces the high-pressure chamber 16, at least partially, with a concave surface 26. In a preferred embodiment, the annular cavity 24 is toroidal, preferably with a circular cross-section.

On the side facing the low-pressure chamber 14 , the plate also has a flat, annular surface 28 and a convex surface 30 adjoining the annular surface 28 internally and concentric therewith.

The convex surface 30 adjoins the concave surface 26 and is preferably connected thereto by means of an annular rim 30' ' . The inlet duct 6, which operatively connects the control apparatus 1 to the pump, extends substantially about a first vertical axis Y-Y and has a non-return valve 34, preferably in the region of an opening 32 of the duct 6 towards the high-pressure chamber 16. In a preferred embodiment, the non-return valve 34 is formed by a disk 36 provided with a circumferential groove 38 which extends in the vicinity of the peripheral rim of the disk and houses a resilient sealing ring 42. Elongate guide elements 40, of which there are preferably three, project from the disk on the side in which the circumferential groove 38 is formed.

The elongate guide elements 40 are suitable for being inserted in the inlet duct 6 of the high-pressure chamber 16 in a manner such that the disk 36 of the non- return valve 34 closes the opening 32 of the inlet duct 6, bringing the sealing ring 42 into abutment with the rim of that opening.

The outlet duct 4 , by means of which the apparatus 1 is connected to the supply network, extends substantially about a second vertical axis Z-Z and houses a slide 44 of a flow switch 46.

In one embodiment, the slide 44 has an elongate cylindrical body 48 which is fixed firmly, at its two ends, to a first flat cylindrical body 50 and to a second flat cylindrical body 52.

The slide is guided for sliding inside the outlet duct 4, along the second vertical axis Z-Z, and can be moved upwards against its own weight in the presence of a predetermined flow of liquid.

In the region of an end portion of the outlet duct

4 which is to be connected to the supply network, the duct 4 has a collar 54 which, when coupled with the first flat cylindrical body 50, forms a space 56 having a predetermined hydraulic resistance.

In particular, the space 56 is of a size such that the hydraulic resistance which arises upon the passage of a predetermined minimum flow value brings about, between a region upstream and a region downstream of the first flat cylindrical body 50, a pressure difference sufficient to overcome the weight of the slide 44.

The flow switch is completed by a first sensor 58 for detecting the position of the slide 44, formed by a first magnet 60 associated with the slide 44 and by a ' first bulb 62 associated with the cylindrical body 8 of the casing 2 and sensitive to the first magnet 60.

The low-pressure chamber 14 is separated from the internal cavity of the. shank 10 by a substantially cup- shaped resilient diaphragm 64 extending about the horizontal axis X-X.

The diaphragm is preferably restrained peripherally between the walls of the cylindrical body 8 and of the shank 10, and is preferably clamped between them by the mechanical connection means 12. On the side facing the low-pressure chamber 14, the diaphragm 64 has a base 65 and a rod 66 which are preferably coaxial with the horizontal axis X-X.

The base 65 has at least one rib 65' facing the low-pressure chamber 14 and projecting axially from the base 65.

In a preferred embodiment, the rib extends in a radial direction on the surface of the base 65 facing the low-pressure chamber 14, becoming thicker in the vicinity of the horizontal axis X-X and thinner in the vicinity of the peripheral rim of the base 65. The base 65 preferably has_. four ribs 65' .

The rod 66 extends centrally from the base 65 along the horizontal axis X-X towards the low-pressure chamber 14 and extends through the opening 18 of the sealing plate 22 into the high-pressure chamber 16.

The rod 66 has a shoulder 68 arranged axially in a manner such as to be disposed beyond the opening 18 of the plate 22 in the high-pressure chamber 16.

On its side facing the opening 18, the shoulder 68 preferably has a housing 70 containing a seal 72.

The shoulder 68, and preferably the base 65, form one embodiment of a closure member 74 for the central opening 18 of the sealing plate 22.

Moreover, in a predetermined axial position, the rod 66 has a second magnet 76 which cooperates with a second bulb 78 associated with the cylindrical body 8 and sensitive to the second magnet 76.

The second magnet and the second bulb form a second sensor 80 for detecting the position of the rod 66 . In a further embodiment of the apparatus, the diaphragm 64 is associated, on the side remote from that from which the rod 66 extends, with a support plate 82 on which a resilient loading means 84 bears.

The resilient loading means is preferably formed by a spring 86 which extends along the horizontal axis X-X, inside the shank 10.

In a preferred embodiment, the resilient loading means 84 can be calibrated by means of an adjustment device 88. In other words, the force of the spring 86 acting on the diaphragm 64 can be varied according to the user's requirements or the characteristics of the pump, on the basis of the adjustment performed on the adjustment device 88. In one embodiment, the adjustment device comprises a block 90 slidable axially on guides 92 fixed to the walls of the shank 10.

In a further embodiment, the slide 90 has a central threaded hole 94 in engagement with a pin 96 fixed firmly to an adjustment knob 98 accessible to the user and disposed at the end of the shank 10.

Rotation of the adjustment knob is preferably facilitated by axial bearings 100.

The diaphragm 64, the rod 66, and the resilient loading means 84, together with the second sensor 80 for detecting the position of the rod 66, form a device which is sensitive to the pressure of a fluid, that is, a pressure switch 102, which can advantageously be calibrated by means of the adjustment device 88. The rod 66 of the pressure switch 102 can adopt two limit positions for each position of the adjustment device 88, that is, for each calibration of the spring 86.

These limit positions of the rod 66 are consequent upon the values adopted by the forces acting on the rod 66 .

The rod 66 is subject to the resilient force produced by the compression of the spring 86, which tends to move the shoulder 68 of the closure member 74 away from the opening 18 in order to bring the ribs 65 ' of the base 65 into abutment with the sealing plate 22 delimiting the opening 18.

The resultant of the forces due to the pressure of the liquid present in the low-pressure chamber 14 and in the high-pressure chamber 16 acts on the diaphragm 64 and on the rod 6, in opposition to this resilient force.

The rod 66 is also subject to the resilient action of the diaphragm 64 which acts in opposition to or with the action of the spring 86, according to the configuration adopted by the diaphragm.

In a first limit position of the rod 66, referred to as the retracted limit position, the rod 66 is in a position in which the shoulder 68 of the closure member

74 shuts off the opening 18 of the sealing plate 22, forming a seal between the high-pressure chamber 16 and the low-pressure chamber 14 (Figure 1) .

In the configuration described, the resultant of the forces produced by the pressure of the liquid present in the low-pressure chamber 14 and in the high- pressure chamber 16 is greater than the resilient force of the spring 86 on the diaphragm 64 so that the rod 66, which is kept in the retracted limit position, causes the shoulder 68 of the closure member 74 to shut off the opening 18, forming a seal between the high-pressure chamber 16 and the low-pressure chamber 14.

In other words, the shoulder 68 of the closure member 74 is urged towards the opening 18 of the sealing plate 22, squeezing the seal 72 housed therein against the annular rim 30' ' of the opening and forming a seal. In the above-described retracted limit position of the rod 66 , the high-pressure chamber 16 and the low- pressure chamber 14 are disconnected with regard to pressure since they are kept separate by virtue of the seal formed by the shoulder 68 of the closure member 74. Moreover, the second sensor 80 of the pressure switch 102 does not send a signal to the pump, since the second bulb 78 is not excited by the second magnet 76 which is fixed firmly to the rod 66 and is disposed remote from the second bulb 78. Finally, the non-return valve 34 is closed, by virtue of the arrangement of the apparatus and of the weight of the valve itself, and the slide 44 of the flow switch 46 is in a lowered position, owing to the absence of a flow towards the supply network. The first sensor 58 for detecting the position of the slide 44 does not send a signal to the pump since the first bulb 62 is not excited by the first magnet 60 which is fixed firmly to the slide 44 and is disposed remote from the first bulb 62. In a second limit position of the rod 66, referred to as the advanced limit position, the rod 66 is in a position in which the base 65 is in abutment with the sealing plate 22 (Figure 3) .

The base 65 is preferably in abutment with the sealing plate 22 by means of the ribs 65 ' of the base 65 so that, since the ribs form means for spacing the base 65 from the opening 18 of the sealing plate 22, they define ducts which leave the high-pressure chamber 16 in communication with the low-pressure chamber 14. In the advanced limit position, the resultant of the forces due to the pressures of the liquid present in the high-pressure chamber 16 and in the low-pressure chamber 14 is less than the force exerted by the spring 86 and by the resilience of the diaphragm 64 so that the rod 66 is kept with the base 65 in abutment with the opening 18 of the sealing plate 22.

Moreover, in the above-mentioned configuration, the second sensor 80 of the pressure switch 102 sends a signal to the pump since the second bulb 78 is excited by the proximity of the second magnet 76 fixed firmly to the rod 66.

The retracted limit position of the rod 66, as described above, defines an operative condition for the apparatus 1 which corresponds to the pump being stopped and the network being under pressure.

The advanced limit position of the rod 66 defines an operative condition for the apparatus 1 which corresponds to lockout of the pump, as described below.

In the event of non-availability of liquid to the pump due, for example, to the drying-out of a basin, the exhaustion of a reservoir, or to the lowering of the level of the liquid in a well, the pump cannot supply liquid to the apparatus so that the resultant of the forces due to the pressure of the liquid in the low- pressure chamber 14 and in the high-pressure chamber 16 adopts a value less than the force of the spring 86 on the diaphragm 64.

In this condition, the flow of liquid towards the supply network is zero so that the slide 44 of the flow switch 46 is in a lowered position. The first sensor 58 for detecting the position of the slide 44, which is not excited, does not send a signal to the pump.

The same advanced limit position of the rod 66 defines an operative condition for the apparatus 1 which corresponds to a lack of liquid pressure in the low- pressure chamber and in the high-pressure chamber, due to leakages towards the supply network.

In fact, if a flow of small magnitude takes place from the apparatus 1 towards the supply network, for example, due to leakages, but is less than a predetermined minimum flow sufficient to lift the slide 44 of the flow switch 46, the pressure of the liquid in the low-pressure chamber 14 falls below the minimum pressure threshold such as to allow the action of the spring 86 to move the rod 66 from the retracted limit position towards the advanced limit position. In this case, the minimum threshold is the restarting threshold.

The same advanced limit position of the rod 66 is also reached by the rod in limit operative conditions of the supply of liquid from the apparatus 1 towards the supply network.

In this condition, the second sensor 80 for detecting the position of the rod 66 sends a signal to the pump. However, in this case, there is a flow of liquid towards the supply network so that the slide of 'the flow switch 46 is in a raised position. The first sensor 58 for detecting the position of the slide 44 sends a signal, since the first bulb 62 of the first sensor 58 is excited by the proximity of the first magnet 60 fixed firmly to the slide.

In the various operative conditions of the apparatus, the signals sent by the first sensor 58 for detecting the position of the slide 44 and by the second sensor 80 for detecting the -position of the rod 66 are controlled by a control circuit (not shown) , for example, an electrical control circuit, which defines an operating logic for the pump, controlling the starting and/or the stopping of a motor with which the pump cooperates . In particular, in the condition in which the pump is stopped and the network is under pressure, for example, when the user does not require fluid from the network, which remains in a condition ready to supply it, neither the first sensor 58 nor the second sensor 80 sends a signal to the electrical circuit so that the apparatus remains in the above-mentioned conditions.

In the lockout condition of the pump, for example, when the pump has no liquid available to supply to the network, the first sensor 58 for detecting the position of the slide 44 sends no signal to the control circuit, whilst the second sensor 80 for detecting the position of the rod 66 sends a signal to the control circuit.

In the presence of a signal from the second sensor

80, the control circuit starts the pump by means of the motor but, if this situation persists beyond a predetermined limit time interval due to lack of liquid, the control circuit locks out the pump.

In the condition in which there is a lack of pressure in the low-pressure chamber due to leakages and losses, for example, because of a leak from a dripping tap, the second sensor 80 sends a signal to the control circuit whilst the first sensor 58 does not send a signal because the flow of liquid is below the predetermined minimum. In these conditions, the control circuit arranges for starting of the pump. Within a short period of time, this starting will result in pressurization of the entire network and in a return of the rod 66 of the pressure switch 102 to the retracted limit position so that the control circuit does not lock out the pump.

In the limit operative condition of the supply of liquid to the supply network, both the second sensor 80 and the first sensor 58 send signals to the control circuit. The signal coming from the flow switch 46 has absolute priority so that the control circuit keeps the pump in operation.

The control circuit is preferably housed in an operating and control box (not shown) outside the apparatus 1 but in the vicinity thereof. The box is accessible to the user to permit the operation of general switches for starting and stopping the apparatus and the pump.

In a configuration in which the pump is in operation and supply is taking place towards the supply network, which corresponds to a situation in which there is a requirement for a flow by the user, the rod 66 of the pressure switch 102 is in an intermediate position between the retracted limit position and the advanced limit position of the rod 66 (Figure 2) . Starting from the configuration in which the pump is stopped and the network is under pressure, a request for a first flow by the user brings about a flow of liquid towards the supply network, which lifts the slide 44 of the flow switch 46 from the lowered position to a raised position.

The flow of liquid through the outlet duct 4 towards the supply network, passing through the space 56 between the first flat cylindrical body 50 of the slide 44 and the collar 54 of the casing 2 generates, between the region upstream and the region downstream of the first flat cylindrical body 50, a pressure difference sufficient to lift the slide 44, against the effect of its own weight .

When the slide 44 is in the raised position, the first magnet 60 fixed to the slide excites the first bulb 62 so that the first sensor 58 for detecting the position of the slide 44 sends a signal to the pump. As already mentioned above, the signal coming from the first sensor 58 has absolute priority so that the control circuit arranges for starting of the pump.

At the same time, the flow of liquid towards the supply network brings about a slight drop in pressure in the low-pressure chamber 14. When the value of the pressure of the liquid in the low-pressure chamber 14 falls below a predetermined pressure threshold, the action of the spring 86, and possibly of the resilience of the diaphragm 64, prevails over the resultant of the forces due to the pressure of the liquid in the low- pressure chamber 14 and in the high-pressure chamber 16. The rod 66 is therefore moved from the retracted limit position to an intermediate position in which the shoulder 68 of the closure member 74 does not shut off the opening 18 of the plate 22.

The fluid transmitted by the pump, which has now started, passes through the apparatus 1 and is supplied to the supply network. However, the fluid is moved from the high-pressure chamber 16 to the low-pressure chamber 14 through a passageway 104 defined between the shoulder 68 of the closure member 74 and the suitably-shaped opening 18.

As it passes from the high-pressure chamber 16 to the low-pressure chamber 14 through the suitably-shaped passageway 104, the fluid undergoes a controlled drop in pressure . A requirement for a second flow of liquid, greater than the first flow requirement, corresponds to a greater distance of the shoulder 68 of the closure member 74 from the opening 18 of the sealing plate 22 and hence to a larger passageway 104 for the flow of the liquid from the high-pressure chamber 16 to the low- pressure chamber 14.

The pressure threshold of the liquid in the low- pressure chamber 14 which brings about a movement of the rod 66 from the retracted limit position to the intermediate position in which the closure member is open can be varied by means of the adjustment device 88 operated by the knob 98.

In particular, a rotation of the knob 98 which results in an movement of the block 90 towards the diaphragm 64 corresponds to an increase in the force generated by the compression of the spring 86 and acting on the diaphragm. This greater resilient force^' corresponds to a higher pressure threshold below which the pressure of the liquid in the low-pressure chamber must fall in order for the rod 66 to be brought from the retracted limit position to the condition in which the closure member is open.

In wholly similar manner, a rotation of the knob 98 which results in a movement of the block 90 away from the diaphragm 64 corresponds to a reduction in the resilient force generated by the compression of the spring 86 and acting on the diaphragm. This lower resilient force corresponds to a lower pressure threshold below which the pressure of the liquid in the low-pressure chamber has to fall to bring about movement of the rod 66 from the retracted limit position.

Unusually, the apparatus according to the invention for controlling starting and stopping of a pump can stabilize the apparent pressure head of the pump towards the user.

In fact, by virtue of the second chamber 16, which communicates with the inlet duct 6 of the casing 2 and has an opening 18 towards the first chamber 14 shut off by the shoulder 68 of the closure member 74 that forms a seal between the first chamber 14 and the second chamber 16, the apparent pressure head of the pump with respect to the user is stabilized upon variations in the flow required by the user.

The pressure head of the pump as a function of the flow delivered by the pump has a downward curve as the flow increases (curve P in Figure 5) and gives rise to a pressure head of the network which is lower than the pressure head of the pump, because of inevitable losses, and which has a wholly similar curve (curve I) . For a network provided with a pump and with the control apparatus according to the invention, experimental tests carried out by the Applicant have shown a pressure head to the user which is characterized by a portion with a substantially constant pressure head, up to a limit flow-rate depending on the pressure head of use that has been set (curve (I+A)ι and (I+A)₂) .

In particular, if the adjustment device is adjusted so as to set a minimum pressure threshold equal to a first pressure p_1# the apparatus connected to the pump can provide, at the first pressure p_x, flow-rates variable between a flow-rate of substantially zero and a first limit flow-rate Qi, the value of which is related to the minimum threshold set (curve (I+A)i).

Naturally, for a flow requirement greater than the first limit flow-rate Q_{l r} these flows will be delivered, but at pressures lower than p_l7 following the characteristic P of the pressure head of the pump until the intrinsic limits of the pump are reached.

In wholly similar manner, if the adjustment device is adjusted so as to set a minimum pressure threshold equal to a second pressure p₂, for example, lower than Pi, the apparatus connected to the pump can provide, at the second pressure p₂, flow-rates variable between a flow-rate of practically zero and a second limit flow- rate Q_2/ which is greater than the first limit flow-rate Qi and the value of which is related to the minimum threshold set (curve (I+A)₂).

In this case also, for a flow requirement greater than the second limit flow Q₂, these flows will be delivered, but at pressures lower than p₂, following the characteristic P of the pressure head of the pump until the intrinsic limits of the pump are reached.

Naturally, the apparatus according to the invention permits an unusual stabilization of the pressure towards the user, which is necessary for correct operation of some domestic user appliances such as washing machines or dishwashers, or industrial appliances such as cooling systems, air-conditioning systems and the like.

Moreover, the apparatus according to the invention, provided with the adjustment device which can act on the resilient loading means, advantageously enables a liquid to be supplied to the supply network at a pressure which is adjustable in accordance with the user's requirements . In particular, the apparatus has the advantage of enabling even an unskilled user to perform this adjustment by operating a knob for adjusting the compression of the spring, in a simple and effective manner. Moreover, the same apparatus, provided with the adjustment device, can advantageously be used for the supply of liquid at different pressures. For example, the same apparatus, connected .to a suitable pump, enables liquid to be supplied to buildings with different numbers of floors.

According to a further advantageous aspect, the apparatus described enables even an unskilled user to adjust the minimum restarting threshold, according to need, in order to prevent emptying of the supply network downstream of the apparatus, avoiding factory intervention on the control apparatus .

Generally, in order to modify this threshold, a factory operation is required to calibrate the pressure switch appropriately, usually by varying the calibration of the sensor associated therewith, in particular, by varying the position of the magnet on the rod.

According to a further advantageous aspect, the control apparatus according to the invention enables the pressure of the liquid supplied to the network to be stabilized, avoiding the need to connect to the apparatus further devices which might interfere with the control functions of the apparatus itself. In other words, the apparatus according to the invention enables the starting and the stopping of the pump to be controlled and its apparent pressure head towards the user to be stabilized, preventing malfunctioning of the network due to construction errors, assembly errors, and errors in the use of such separate devices, for example, a calibration of such separate devices which is inconsistent with the operating characteristics of the control apparatus .

For example, in connecting a control apparatus to a separate pressure-adjustment device disposed upstream of the apparatus, it is possible, owing to errors of construction, assembly, or use, for the starting of the pump, which is brought about by the apparatus on the basis of pressure or flow conditions in the apparatus itself, not to correspond to a configuration of the pressure-adjustment device which permits a free flow of fluid from the pump towards the apparatus . In a further example, the apparatus according to the invention avoids the need for a connection to a separate pressure-adjustment device disposed downstream of the apparatus which, by shutting off the flow of liquid from the apparatus to the supply network, even only partially, generates a malfunction of the flow switch.

Finally, the overall structure of the apparatus according to the invention is compact and simple and, to sum up, reliable.

Naturally, in order to satisfy contingent and specific requirements, a person skilled in the art may apply to the above-described apparatus many modifications and variations all of which, however, are included within the scope of protection of the invention as defined by the appended claims.

Claims

1. Apparatus (1) for controlling the starting and stopping of a pump in a liquid-supply network, comprising a casing (2) which can be operatively associated with the supply network by means of an outlet duct (4) and which can be operatively associated with the pump by means of an inlet duct (6) , the casing comprising: a first chamber in communication with the outlet duct (4) of the casing (2) , a pressure switch (102) for sending a signal to the pump in the presence of at least one threshold value of the pressure of the liquid in the first chamber, and a flow switch (46) for sending a signal to the pump in the presence of a predetermined minimum flow of liquid towards the supply network, the apparatus (1) being characterized in that the casing (2) also comprises a second chamber (16) in communication with the inlet duct (6) of the casing (2) and having an opening (18) towards the first chamber

(14), and further comprises a closure member (74) which can shut off the opening (18) and can form a seal between the first chamber (14) and the second chamber (16) .

2. Control apparatus (1) according to Claim 1 in which the first chamber (14) forms a low-pressure chamber for holding liquid at low pressure and the second chamber (16) forms a high-pressure chamber for holding liquid at high pressure.

3. Control apparatus according to Claim 1 or Claim 2 in which the opening (18) between the second chamber (16) and the first chamber (14) is shaped by a concave surface (26) and a convex surface (30) in series.

4. Control apparatus according to Claim 3 in which the concave surface faces towards the second chamber (16) and the convex surface faces towards the first chamber (14) .

5. Control apparatus according to Claim 3 or Claim 4 in which the convex surface is the base of an annular cavity (24) formed in a sealing plate (22) which separates the second chamber (16) from the first chamber (14) .

6. Control apparatus according to any one of the preceding claims in which the closure member (74) is fixed firmly to the pressure switch (102) .

7. Control apparatus according to any one of the preceding claims in which the closure member (74) comprises spacer means for defining a position of maximum distance of the closure member from the opening (18) of the sealing plate (22) .

8. Apparatus according to Claim 7 in which the spacer means comprise a base (65) .

9. Apparatus according to Claim 7 or Claim 8 in which the spacer means comprise ribs (65') .

10. Apparatus according to Claim 9 in which the ribs (65') are fixed firmly to the base (65) .

11. Control apparatus according to any one of the preceding claims in which the closure member comprises a shoulder (68) which houses a seal (72) .

12. Control apparatus according to any one of the preceding claims in which the pressure switch (102) can be calibrated by operating on resilient loading means

(84) .

13. Control apparatus according to Claim 12 in which the resilient loading means (84) is formed by a spring (86) .

14. Apparatus according to Claim 12 or Claim 13 in which the resilient loading means is adjustable by operation of an adjustment device (88) .

15. Apparatus according to Claim 14 in which the adjustment device comprises a sliding block (90) on which the resilient loading means (84) bears.

16. Apparatus according to Claim 15 in which the block (90) is slidable on guides (92) .

17. Apparatus according to Claim 15 or Claim 16 in which the adjustment device (88) comprises a knob (98) the rotation of which causes sliding of the block (90) .

18. Apparatus according to any one of the preceding claims in which the flow switch (46) comprises a slide

(44) which, in a lowered position, defines, with a collar (54) fixed firmly to the outlet duct (4) , a space (56) suitable for bringing about a pressure difference between a region upstream and a region downstream of the slide, upon the passage of a predetermined minimum flow of liquid.

19. Control apparatus according to Claim 18 in which the slide (44) is formed by an elongate, cylindrical body (48) fixed firmly, at its ends, to a first flat cylindrical body (50) and to a second flat cylindrical body (52) .

20. Control apparatus according to Claim 18 or Claim 19 in which the flow switch (46) comprises a first sensor (58) for detecting the position of the slide (44) .

21. Control apparatus according to Claim 20 in which the first sensor for detecting the position of the slide comprises a first magnet (60) fixed firmly to the slide (44) and a first bulb (62) fixed firmly to the casing (2) .

22. Control apparatus according to any one of the preceding claims, further comprising a non-return valve (34) suitable for shutting off the inlet duct (6) of the casing (2) .

23. Control apparatus according to Claim 22 in which the non-return valve comprises a disk (36) which can close the inlet duct (6) and from which elongate guide elements (40) of the disk (36) extend.

24. Control apparatus according to any one of the preceding claims in which the pressure switch (102) comprises a rod (66 ) fixed to the closure member (74) .

25. Control apparatus according to Claim 24 in which the rod (66) can adopt a retracted limit position in which the closure member (74) closes the opening (18) , forming a seal between the first chamber (14) and the second chamber (16) , and an advanced limit position in which the closure member (74) does not close the opening .

26. Apparatus according to Claim 25 in which, in the advanced limit position, the closure member (74) is in abutment with the plate (22) , adopting a position of maximum distance from the opening (18) of the plate by means of spacer means (65')^".

27. Apparatus according to any one of the preceding claims in which the pressure switch (102) further comprises a second sensor (90) for detecting the position of the rod (66) .

28. Apparatus according to Claim 27 in which the second sensor (90) comprises a second bulb (78) fixed firmly to the casing (2) and a second magnet (76) fixed firmly to the rod (66) .

29. Apparatus according to any one of the preceding claims in which the signals of the flow switch (46) and of the pressure switch (102) are sent to a circuit for controlling the starting and/or stopping of the pump, which circuit controls a motor that cooperates with the pump.

30. Control apparatus according to Claim 29 in which the control circuit is housed in a control and operating box outside the apparatus (1) and in the vicinity thereof .

31. Control apparatus according to any one of the preceding claims in which the flow switch (46) is disposed in the outlet duct (4) in order to shut off the flow of liquid towards the network.