EP1431583A2

EP1431583A2 - Device for actuating electric pumps in liquid distribution systems

Info

Publication number: EP1431583A2
Application number: EP03027457A
Authority: EP
Inventors: Dario Bedin; Bruno Franchetti; Ruby Cegalin
Original assignee: DAB Pumps SpA
Current assignee: DAB Pumps SpA
Priority date: 2002-12-20
Filing date: 2003-12-01
Publication date: 2004-06-23
Anticipated expiration: 2023-12-01
Also published as: DE60309123D1; EP1431583B1; ATE343066T1; DE60309123T2; EP1431583A3; ITPD20020330A1; ES2274162T3

Abstract

A device for actuating electric pumps for water distribution systems, comprising a hollow hydraulic body (10), to be associated with an electric pump (11) with a single-phase electric motor, which forms internally a main duct (18) with end connectors (19, 20) for connection to the hydraulic system, the main duct (18) containing a flow-controlled switch (21), which cooperates with a pressure sensor (29) that is associated with the body (10) and is coupled to an electronic pressure reduction unit that operates by reducing the rotation rate of the motor according to a voltage variation chosen between one produced in the main winding and one in the electrical power supply line.

Description

The present invention relates to a device for actuating electric pumps in liquid distribution systems.

The device is used particularly but not exclusively in water distribution systems.

In the field of actuation devices for electric pumps, currently there is a subset of various systems that can be divided mainly into three large families: pressure-controlled actuation devices, pressure- and flow-controlled actuation devices, and constant-pressure actuation devices (using an inverter).

Pressure- and flow-controlled actuation provides for the presence of a flow sensor (flow-controlled switch), which is generally of the ON/OFF type in order to determine the flow "0" (reference flow with maximum pressure) and of a pressure sensor for measuring the "start P" or the pressure that must start the pump.

Pump starting occurs in two manners:

due to flow, when an immediate request for flow (greater than the set flow-rate limit, set for example at approximately 3 l/min) arrives from the system, for example upon opening a faucet;
due to pressure, when somewhere in the system dripping occurs or there is a small demand for flow (lower than the set flow-rate limit, which is set for example at approximately 3 l/min), causing a decrease in pressure.

The pump stops instead only due to flow, i.e., the flow-controlled switch checks whether the "0" flow state, or a flow-rate in the system that is lower than the set flow-rate limit, has been reached.

Although this type of actuation is commonly used and widespread because it has a simple structure and adjustment, it still has unresolved problems.

For example, if the combined pressure- and flow-controlled switch always stops at the "P max" point, which corresponds to the "0" flow point, this means that the system is constantly kept at the maximum pressure generated by the pump.

If the pump in the system is oversized or there is poor control of the pressure in input to the pump (as frequently occurs in domestic systems), a situation can occur in which the "max P" is too high and causes severe consequences for the tightness of the safety valves of sanitary fixtures, with the onset of intense stresses affecting various devices and with possible flooding.

The aim of the present invention is to provide a device for actuating electric pumps for water distribution systems that solves the above-noted drawbacks of the prior art.

Within this aim, an object of the present invention is to provide a device for actuating electric pumps for water distribution systems that achieves the effect of reducing the pressure without causing any load loss.

Another object of the present invention is to provide a device for actuating electric pumps for water distribution systems that reduces the pressure only close to the maximum pressure, maintaining unchanged efficiencies and performance in the remaining operating range of the pump.

Another object of the present invention is to provide a device for actuating electric pumps for water distribution systems that is physically a separate module that can be applied without difficulty to a standard pump in order to convert it into a controlled-actuation pump.

This aim and these and other objects that will become better apparent hereinafter are achieved by a device for actuating electric pumps for water distribution systems, characterized in that it comprises a hollow hydraulic body, to be associated with an electric pump with a single-phase electric motor, which forms internally a main duct with end connectors for connection to the hydraulic system, said main duct containing a flow-controlled switch that cooperates with a pressure sensor that is associated with said body and is coupled to an electronic pressure reduction unit that operates by reducing the rotation rate of the motor according to a voltage variation chosen between one produced in the main winding and one in the electrical power supply line.

Further characteristics and advantages of the present invention will become better apparent from the following detailed description of a preferred but not exclusive embodiment thereof, illustrated by way of nonlimiting example in the accompanying drawings, wherein:

Figure 1 is a first sectional view, taken along a longitudinal plane, of a device according to the invention;

Figure 2 is a second sectional view, taken along the line II-II of Figure 1;

Figure 3 is a third sectional view, taken along the line III-III of Figure 1;

Figure 4 is a Q-H flow-rate/head (pressure) chart of a pump provided with the device according to the invention;

Figures 5 and 6 are views of two steps of the fitting of the device according to the invention on a pump.

With reference to the figures, a device for actuating electric pumps for water distribution systems comprises a hollow hydraulic body, generally designated by the reference numeral 10, to be associated with an electric pump 11, as will become better apparent hereinafter, that has a single-phase electric motor.

The hydraulic body 10 is provided with a small compensation chamber 12, formed by a membrane 13 that is arranged so that its edges lie on an opening 14 thereof with a flange 15 and by a cambered cover 16 that closes the assembly and is fixed to the flange 15 by means of screws 17.

The membrane 13 is interposed and fixed by means of the edges between the flange 15 and the cover 16.

The hydraulic body 10 forms internally a main duct 18 whose axis is perpendicular to the axis of the cover 16, with

end connectors

19 and 20 for connection to the hydraulic system, which is not shown in the figures for the sake of simplicity.

A flow-controlled switch 21 is arranged in the main duct 18 and is constituted by a disk-like flow control element 22 with a sealing ring 23 that acts on a seat 24 of the body 10.

The flow control element 22 has, on one side, longitudinal peripheral tabs 25 for guiding in the duct 18 and, on the opposite side, an axial stem 26 that is surrounded by a cylindrical helical spring 27, which is compressed between the flow control element and a tubular element 28, which is arranged in the duct 18 and in which the stem 26 passes; said spring pushes said flow control element so that it forms a seal against the seat 24.

A per se known analog pressure sensor 29 is arranged in a seat 30 formed in a protrusion 31 of a half box-like body 32, which is fixed by means of screws 33 to the hydraulic body 10 at right angles to the chamber 12 and parallel to the longitudinal axis of the duct 18.

The analog pressure sensor 29 is connected to the hydraulic body 10 by means of a first secondary duct 34, which is formed in the protrusion 31 and includes a temperature sensor of the NTC type, not shown in the figures.

Sealing rings 35 are arranged between the protrusion 31 and the hydraulic body 10.

In order to have an exact pressure measurement, the sensor 29 is connected, on the opposite side with respect to the first secondary duct 34, to the atmospheric pressure by means of a second secondary duct 36 arranged in the half box-like body 32.

The assembly of the pressure sensor 29 rests on an electronic board 37, which is fixed inside the half box-like body 32.

The electronic board 37 comprises an electronic pressure reduction unit (not shown in the figures), which reduces the pressure by reducing the rotation rate of the electric motor without causing any load loss (differently from mechanical pressure reduction units).

Pressure reduction occurs only in the region that is considered "critical", i.e., close to the maximum pressure, maintaining unchanged performance and efficiencies over the remaining "actual" operating range of the pump.

The reduction of the rotation rate of the motor occurs solely by varying the voltage of the main winding of said motor, which is of the single-phase type.

A version that acts by varying the voltage of the power supply line is also provided.

More particularly, the voltage variation is achieved by reducing the waveform of the voltage, by means of a triac 38, or by reconstructing the amplitude of the waveform of the voltage by means of a MOSFET (PWM technology), not shown.

Since both are crossed by the current, they overheat due to the Joule effect and therefore must be cooled.

In the field of electronics, this component is usually cooled by convection, i.e., by means of an aluminum fin that is fixed mechanically to it.

In the case of the device according to the invention, the triac 38 has dynamic cooling, which is provided by resting it on a brass insert 39 located in the hydraulic body 10 in contact with the pumped liquid.

In order to provide insulation between the triac 38 and the insert 39, a layer and preferably two or more layers 40 are interposed, necessarily according to the standards with a thickness of 1 mm each, and are made of alumina, a material that has a high insulating power while maintaining good heat conductivity.

As regards operation, by means of the sensor 29 the pressure is read, and by interpolating the value of the voltage variation with the value of the pressure, the curve charted in dashed lines in Figure 4 is obtained (varying from the continuous solid curve of the pump in standard operation).

With continuous and automatic updating of the reading of the pressure data, by interpolating the voltage variation, the system is able to vary the rotation rate of the motor and accordingly to keep constant for example the value P max - 20% until the original performance of the curve is rejoined.

By means of a trimmer (not shown in the figures) for adjusting the pressure portion between P max and P max -20%, it is possible to reduce or keep normal the pressure provided by the pump.

To protect the pump against ice, when the device according to the invention, by means of the temperature sensor integrated in the pressure sensor 29, detects an internal temperature that is lower than a set value, for example +2-3 °C, by means of a control performed by means of a microcontroller, the device launches a series of forced activations in order to keep the liquid inside the pump in motion, thus preventing its freezing and consequent crystallization.

As the temperature decreases, the forced activations are increasingly frequent and longer, according to settings determined beforehand on the microcontroller during the manufacturing process, protecting the pump to a limit temperature of for example -10°C.

The device according to the invention (Figures 5 and 6) is contained in a box-like module 50, which can be applied to a standard pump 11 in order to convert it into a controlled-actuation pump by means of the simple operations of removing a terminal strip cover 41 of the standard pump 11, applying a coupling connector 42 to the pump 11, and fitting the module 50, thus obtaining an automatic and compact product by means of simple operations.

In practice it has been found that the described invention has solved the drawbacks noted in the prior art.

A device for actuating electric pumps for water distribution systems has in fact been provided which achieves the effect of reducing the pressure without causing any load loss.

The pressure is kept at levels that have no consequences for the tightness of the safety valves of the sanitary fixtures and do not cause intense stresses affecting various devices.

The device reduces the pressure only close to the maximum pressure, maintaining unchanged efficiencies and performance in the remaining range of operation of the pump.

The device, moreover, is physically an independent module that can be applied without difficulty to a standard pump in order to convert it into a controlled-actuation pump.

The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims; all the details may further be replaced with other technically equivalent elements.

In practice, the materials employed, so long as they are compatible with the specific use, as well as the dimensions, may be any according to requirements and to the state of the art.

The disclosures in Italian Patent Application No. PD2002A000330 from which this application claims priority are incorporated herein by reference.

Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

A device for actuating electric pumps for water distribution systems, characterized in that it comprises a hollow hydraulic body (10), to be associated with an electric pump (11) with a single-phase electric motor, which forms internally a main duct (18) with end connectors (19, 20) for connection to the hydraulic system, said main duct (18) containing a flow-controlled switch (21) that cooperates with a pressure sensor (29) that is associated with said body (10) and is coupled to an electronic pressure reduction unit that operates by reducing the rotation rate of the motor according to a voltage variation chosen between one produced in a main winding of the motor and one in the electrical power supply line.
The device according to claim 1, characterized in that said pressure sensor (29) is analog and located in a seat (30) that is formed in a protrusion (31) of a half box-like body (32), which is fixed by means of screws (33) to said hydraulic body (10) that is parallel to the longitudinal axis of said main duct (18), said pressure sensor (29) being connected to said hydraulic body (10) by means of a first secondary duct (34), which is formed in said protrusion (31), and being connected, on the opposite side with respect to said first secondary duct (34), to the atmospheric pressure by means of a second secondary duct (36) that is arranged in said half box-like body (32).
The device according to claim 1, characterized in that said analog pressure sensor (29) includes a temperature sensor.
The device according to claim 2, characterized in that the assembly of said pressure sensor (29) rests on an electronic board (37), which is fixed inside said half box-like body (32) and comprises said electronic pressure reduction unit.
The device according to claim 1, characterized in that said voltage variation is achieved by choosing between the methods of reducing the waveform of the voltage by means of a triac (38) and of reconstructing the amplitude of the waveform of the voltage by MOSFET (PWM technology).
The device according to claim 5, characterized in that said triac (38) or MOSFET is cooled by contact against a metallic insert (39) that is present in said hydraulic body (10) in contact with the pumped liquid.
The device according to claim 6, characterized in that at least one layer (40) of alumina is interposed between said triac (38) or MOSFET and said insert (39).
The device according to claim 1, characterized in that it comprises a trimmer for adjusting the setting of the maximum actual pressure for controlled operation of said pump (11).
The device according to claim 1, characterized in that said hydraulic body (10) is provided with a compensation chamber (12) whose axis is perpendicular to the axis of said main duct (18), said chamber being formed by a membrane (13) that is arranged on one of its openings (14) with a flange (15) and by a cambered cover (16), which closes the assembly and is fixed by means of screws (17) to the flange (15).
The device according to one or more of the preceding claims, characterized in that if said temperature sensor integrated in said pressure sensor (29) detects an internal temperature that is lower than a set temperature, by means of a control performed by a microcontroller, it launches a plurality of forced activations set during the manufacturing process, in order to keep the liquid inside the pump in motion, thus preventing it from freezing and consequently crystallizing.
An electric pump, characterized in that it comprises a device according to one or more of the preceding claims.