EP0901654A1

EP0901654A1 - A self-regulating computerized proportional control device for a water pump

Info

Publication number: EP0901654A1
Application number: EP98905610A
Authority: EP
Inventors: Vincenzo Consoli; Roberto Gigliotti; Luciano Masini; Luca Pinori
Original assignee: Hydroservice SRL
Current assignee: Hydroservice SRL
Priority date: 1997-02-13
Filing date: 1998-02-13
Publication date: 1999-03-17
Also published as: ITPI970009A0; IT1295577B1; ITPI970009A1; WO1998036339A1

Abstract

A self-regulating computerized proportional device controlling a water pump comprises a body (1) connected hydraulically to the delivery line of the pump and an outlet section from which water flows to the system served by the pump. The inside of the body accommodates a flow sensing and flow check device (5), and a pressure sensor (11) consisting in a Bourdon tube coupled to a rotary encoder (14). Output signals from the flow and pressure sensors are supplied to a microprocessor (17) by which the pump is started and stopped both in response to the information contained in the signals and according to operating sequences determined on the basis of previously programmed instructions.

Description

TITLE A SELF-REGULATING COMPUTERIZED PROPORTIONAL CONTROL DEVICE

FOR A WATER PUMP DESCRIPTION Field of the Invention

The present invention relates to a device for controlling a water pump. Description of the Prior Art

In any hydraulic system where water is supplied by means of an electric pump, the pump must switch on, deliver water under pressure and then switch off to discontinue the flow of water, in response to the demand from users of the system. The transmission of start and stop control signals to the electric pump is one of the principal problems encountered in the design and management of water distribution systems, given that such pumps have to guarantee a supply to users while maintaining a running speed compatible with their operating specifications: the fundamental need to avoid over-frequent starting and stopping of the pump in this connection is well known to persons skilled in the art. The problem has been addressed hitherto by adopting substantially two types of system.

A first system makes use of a switch operated by pressure pulses which activates and deactivates the electric pump between minimum and maximum pressure values detected in the water main; the switch is associated to a liquid accumulator with an air-loaded flexible diaphragm with the function of extending the intervals of time between the pump cutting in and cutting out. The drawbacks associated with this system are well known and can be summarized mainly as: high installation and maintenance costs, limited scope of usefulness, and the risk of the water becoming polluted as the result of bacteria ^"proliferating on the diaphragm. In a second type of arrangement that has become popular more recently, use is made of an electric or electronic control system incorporated into a fluid-tight housing with a water inlet and a water outlet, designed for installation directly on the pump delivery line. Many devices responding to this basic type have been patented by various companies, and all possess certain common basic features: compact construction, minimum pressure sensed by a diaphragm pressure switch coupled to a transducer, flow sensed by a spring loaded valve that functions also as a means for maintaining pressure internally of the device and of the circuit as a whole, and management of the system utilizing a combination of pressure control and flow control.

The features in certain of these systems are more evolved. Such as the device disclosed in European Patent n° 219 360, for example, in which the pump is controlled by a pressure sensor consisting in a diaphragm counterbalanced by compressed air and associated to a piston to which a magnet is mounted; the movement of the magnet toward or away from a transducer brings about the activation or deactivation of the pump through the Hall effect. The pump is kept running by virtue of being interlocked to the signal emitted by a spring returned flow control and check valve incorporating a further magnet of which the movement is detected by a stationary sensor. The pump is also prevented from running dry.

A device disclosed in Italian patent application n° MI91A 002777 is substantially similar, the only significant differences being that the diaphragm is counterbalanced by a spring and that the flow control and check valve has no return spring and therefore can be installed only in the vertical position. Finally, in a device of the same type made by the Italian company RITEC S.r.l., the flow control valve is replaced by a pulse turbine, again in conjunction with a Hall effect transducer.

Devices identifiable as being of this second type betray the fundamental drawback likewise that the function of sensing a minimum pressure is entrusted to a flexible diaphragm, with all the problems that such a solution entails. Often the diaphragm will rupture, leaving the pump unable to operate. Also, with the diaphragm affording a site on which water can stagnate, there is the risk that bacteria will proliferate and ultimately pollute the main supply. With a diaphragm moreover, it is either impossible to regulate the minimum pressure at which the pump restarts, or possible only within extremely tight bands of values; this means that the device must be selected initially according to the specifications of the system in which it is required to operate. In effect, if the pressure bearing on the diaphragm from the column of water above is greater than the minimum restart set point, the pump will never come into operation. Finally, in order to counterbalance the water pressure in the apparatus, the diaphragm must be preloaded either with compressed air or by a spring; this causes considerable stresses, resulting in wear and in loss ultimately of the correct set points .

A further drawback affecting all the above mentioned systems is their inability to recognize a drop in pressure caused not by effective user demand, but rather by small leaks which cause the pump to cut in continually and replenish the loss, wasting both water and energy.

Finally, a third drawback common to all of the systems mentioned is that, following activation of the device which protects the pump against running dry, the pump cannot restart automatically once the delivery line^' has again filled with water. Summary of the Invention

A first object of the present invention is to provide a control device for a water-pressurizing electric pump unaffected by the drawbacks mentioned above, and in particular a device that makes no use of a diaphragm type pressure sensing element. A further object of the present invention is to provide a device of the aforementioned type such as will monitor pressure continuously, identifying and responding automatically to a variety of situations that may arise during the operation of the system served by the pump, including structural changes to the system itself.

These objects have been achieved with the control device for an electric pump according to the present invention, which comprises a body hydraulically connectable to the delivery side of the pump and to an outlet section from which water flows to the system which has to be fed. The body accommodates a flow sensing and flow check means . Pressure is sensed by a gauge element associated with the outlet section and capable of generating digital information that will be a function of the pressure sensed within the section. The output signals from the flow and pressure sensing elements are managed by a microprocessor that pilots the activation and deactivation of the pump in response to these signals and on the basis of previously programmed instructions. Brief description of the drawings

For a fuller appreciation of the features and advantages afforded by the control device for an electric pump according to the present invention, a preferred embodiment will now be described by way purely of example and implying no limitation with reference to the accompanying drawings, in which:

-figure 1 is a median longitudinal section of the device according to the invention, viewed in an operating position assumed when there is no flow present; -figure 2 is a longitudinal section identical to that of figure 1, illustrating the device in an operating position assumed when flow is present;

-figure 3 illustrates a pressure sensing means associated with the outlet section of the device;

-figure 4 illustrates a possible flow diagram for a microprocessor resident program. Description of the preferred embodiment

With reference to the above figures, the device according to the present invention comprises a body 1 having a tubular portion la of varying section and an open housing lb extending from one side of the tubular portion. The tubular portion la presents an internally threaded portion of larger section lc, coinciding with the water inlet, and an externally threaded portion of smaller section Id that coincides with the water outlet. Also associated with body 1 is a cylindrical sleeve 2, screwed into and coaxial with the endmost part of the inlet section lc of body 1 in such a way substantially as to form an extension of said section; an O-ring 3 is fitted to the outer surface of sleeve 2 ensuring a fluid tight coupling.

Inside sleeve 2 and section lc of body 1 two internal seats 4 are formed, disposed coaxial with one another and both with sleeve 2. The larger section lc of body 1 houses a check valve 5 consisting in a stem 5a axially free accomodated within seats 4, and a circular plate 5b coaxial with stem 5a, of which the diameter is marginally greater than the bore of sleeve 2. Plate 5b is breasted tightly with sleeve 2, so as to prevent water from flowing through the bore, by a conical coil spring 6 mounted around stem 5a between plate 5b and seat 4 in section la. The side of plate 5b contacting sleeve 2 is provided with a seal 7. A permanent magnet 8 is mounted to the end of a radial arm 5c extending upwards from stem 5a. Housing lb accomodates a pressure gauge 11 of substantially conventional embodiment, consisting in a Bourdon tube, which is connected externally to section Id by way of a threaded cylindrical metal element 11a, sealingly engaging, by way of an O-ring 10, in a threaded hole 9 formed through the wall of section Id. Element 11a affords a pressure sensing duct 12 interconnecting the bore of section Id with the bore of Bourdon tube lib, which extends from cylindrical element 11a. A precision mechanism lie is pivotally associated with the end of the Bourdon tube, and in its turn engages in meshing contact by way of a toothed sector lid with the lateral surface of a cylindrical pin 13, pivotally supported by an inside wall of housing lb, of which the free end carries a rotary encoder 14.

Also accomodated within housing lb, directly alongside and at right angles to the surface of encoder 14, is an electronic circuit board denoted 15 carrying a number of components of which the specific functions will be described hereinafter: an optical sensor 16 positioned in such a way as to read encoder 14; a microprocessor 17; a reset button 18; three light emitting diodes 19; and a Hall effect transducer 20 positioned in such a manner as to ensure its exact alignment with magnet 8 when check valve 5 is closed. Finally, the necessary wires are routed through an access hole 21 afforded by one wall of housing lb.

Housing lb is fitted with a cover 22 and an interposed seal 23, secured by means of screws 24. Projecting from the inside face of cover 22 are a set of light guides 25, positioned in alignment with LEDs 19 and capped by lens elements 26, by which the glow from LEDs is conveyed to the surface, and also a pin 27, positioned in alignment with reset button 18, providing the means by which to depress the button, exploiting the limited flexibility of cover 22. The operation of the control device according to the invention is the following. Supposing that the device is being activated for the first time and therefore that the water system served by the electric pump is empty, the pump is activated by depressing reset button 18, whereupon water coming from the pump enters body 1 by way of sleeve 2 connected to the inlet section, displacing check valve 5 as shown in figure 2. The displacement of the valve causes magnet 8 to move away from the Hall effect transducer 20, which trasmits a signal to the electric motor, to keep the pump into operation. Downstream of check valve 5, a part of the pressurized flow of water passes into sensing duct 12 from section Id of body 1 then up through cylindrical element 11a into Bourdon tube lib. The tube undergoes a deformation, causing a shift of mechanism lie and sector lid that causes pin 13 to rotate about its axis, and with it encoder 14. The movement of encoder 14 creates digital combinations that are decoded by optical sensor 16, the sensor in turn being connected to microprocessor 17 which is able as a result to receive signals corresponding to the pressure sensed through the gauge. The analysis of these signals allows to pilot the operation of the pump on the basis of a previously installed program. The water leaves the device through section Id and is directed into the circuit served by the pump.

Once the system is fully pressurized, water will cease flowing into the device and check valve 5 can be returned by the action of spring 6 to the position of fig 1, in which the inlet is closed by plate 5b and pressure maintained within the system. In this configuration, with magnet 8 and transducer 20 in alignment, a deactivating signal is transmitted to the electric motor and the pump will shut off, though following a delay of so many seconds

(programmable by the user) . The delay ensures that the pump is given time to restore full pressure in the system before shutting off. At this point the encoder stays put on the combination most recently formulated, representing maximum pressure with the pump operating and the check valve closed. If a tap is turned on and pressure in the system then falls below a minimum set point, this will be sensed by way of the encoder and the pump restarted so that pressure is restored.

Microprocessor 17 is programmable, as already said, in such a way as will enable the device to perform a range of self-regulating and self-test functions: identifying a shutdown caused by the pump running dry and thereafter entering a control sequence to reset and restart the pump; self regulation of the minimum pressure set point at which the pump cuts in; detection of leaks from the system. As to the type of program suitable for managing the aforementioned functions, one example is given in the flow diagram of figure 4; the diagram in question will be readily understood and interpreted by a person skilled in the art, and therefore no further description is given.

In the event that the pump inlet line should dry up in operation, check valve 5 closes, bringing magnet 8 into alignment with transducer 20, and encoder 14 will indicate a pressure value below the minimum set point. This combination of two signals relayed to the microprocessor activates the procedure indicated in block B of the flow diagram in figure 4. First, the electric motor is isolated from its power supply to obviate any risk of damage caused by the pump running dry. The microprocessor then executes a self-test routine to verify whether or not there may be any electrical faults, before initiating a user programmable sequence of attempts to restart the pump and re-establish pressure in the system. If these attempts end in failure, the device will lock up and generate signals serving in the example of figure 4 to light up the indicator LEDs 19; other alternative and/or parallel acoustic warning systems might be adopted to equally good effect . Once the water returns, normal operating conditions can be reinstated by pressing the reset button 18.

The selection of self-regulating parameters or settings at the moment of installation is simple, as indicated in block A of the diagram in figure 4; pressing and holding the reset button 18 for a given time, the microprocessor activates the pump and memorizes the pressure registering in the column above the device as the water reaches the tap located highest up in the system, which will have been opened beforehand. The minimum pressure set point at which the pump cuts in will then be established at a value exceeding the memorized value by a given programmable amount .

Finally, the microprocessor is also capable of detecting leaks in the system. As shown in block C of the flow diagram, the microprocessor keeps a statistical record of the starts made by the pump, and on detecting any recurring pattern over a predetermined lapse of time, even with intervals of high consumption suggesting water demands from the users, will proceed to indicate the possible existence of a leak by generating an alarm signal to activate a visual indicator (LED 19) or a sounder.

Whilst reference is made in the depicted embodiment to a Bourdon tube type of pressure gauge and to an optically scanned absolute encoder, these might well be replaced respectively by gauges of equivalent effectiveness (other than those falling with the category of diaphragm types as embraced by the prior art) , and by different transducing elements affording similar performance characteristics.

It will be clear from the present disclosure that the device according to the invention represents a significant step forward in the state of the art, resolving as it does a whole series of problems in devices as used hitherto for the same purpose, and affording additional features of great usefulness .

Variations and/or changes may be made to the device for controlling a water pump according to the present invention, without prejudice to the protection afforded under the appended claims .

Claims

1) A control device for a water pump, comprising a body (1) with an inlet section and an outlet section hydraulically connectable to the pump delivery line, flow sensing and flow check means (5, 8, 20) located within said body (1), and pressure sensing means (11, 12, 13) associated with the outlet section of said body (1) , wherein signals produced by the flow and pressure sensing means are used to pilot the operation of the pump, characterized in that said pressure sensing means comprise a gauge element (11) generating digital output information that is a function of the sensed pressure value, and in that it comprises means (15, 17) for processing the signals and the digital information to activate and deactivate the pump on the basis of previously programmed instructions.

2) A device according to claim 1, wherein said gauge element (11) comprises a Bourdon tube (lib) deformable flexibly under hydraulic pressure, and an optically scanned absolute encoder (14) turnable about its own axis and connected to said Bourdon tube (lib) in such a way that the deformation of the tube causes the rotation of the encoder.

3) A device according to the previous claims, wherein said instructions programmed into said processing means (15, 17) operate as indicated in block A of the flow diagram of figure 4 to the end of establishing its setting.

4) A device according to the previous claims, wherein said instructions programmed into said processing means (15, 17) operate as indicated in block B of the flow diagram in figure 4 to the end of inhibiting the operation of the pump if running dry, and restarting the pump when the water returns thereafter.

5) A device according to the previous claims, wherein said instructions programmed into said processing means (15, 17) operate as indicated in block C of the flow diagram in figure 4 to the end of detecting leaks of water from the system.

6) A device according to the previous claims, wherein a single push button (18) is provided for activating the operation of said instructions.

7) A device according to the previous claims, wherein means (19) for visually and/or acoustically indicating faulty operations of said pump are provided.

8) A device according to the previous claims, wherein said pressure sensing means (11, 12, 13) are accomodatedd in a sealed housing (lb), means (22, 25, 26) being provided for monitoring and controlling said pressure sensing means (11, 12, 13) from externally of said housing (lb) .