A VALVE UNIT FOR REGULATING THE FLOW-RATE OF FUEL GAS IN DEPENDENCE ON THE FLOW-RATE OF WATER, PARTICULARLY FOR WATER HEATERS

Abstract: A valve unit (1) for regulating the flow-rate of a fuel gas in dependence on the flow-rate of water, particularly for water-heaters, comprises a valve (11) for regulating the flow-rate of the fuel gas and a hydraulic turbine (2) which in turn includes a rotor (2a), the rate of rotation of which is associated with the flow-rate of water. The hydraulic turbine (2) is connected to the regulation valve (11) in order to regulate the flow-rate of the fuel gas in dependence on the flow-rate of water supplied to the turbine.

Description: A VALVE UNIT FOR REGULATING THE FLOW-RATE OF FUEL GAS IN DEPENDENCE ON THE FLOW-RATE OF WATER, PARTICULARLY FOR WATER HEATERS Description Technical field The present invention relates to a valve unit for regulating the flow-rate of fuel gas in dependence on the flow-rate of water, particularly for water-heaters, according to the preamble to the main claim. Background art A valve unit including these characteristics is known from European patent No. 240394. This valve unit in fact has a turbine which is driven by a fraction of the water flow supplied in order to operate an electric-current generator used for lighting a pilot flame. The present invention is applicable, in particular but not exclusively, to the field of instantaneous domestic water-heaters in which a fuel gas is supplied to a burner in order to heat water for hygiene purposes . In water-heaters of this type the supply of the fuel gas is arranged to take place only in proportion to a supply of hot water. Naturally, in order to heat the water to a temperature which is independent of its flow-rate, it is necessary correspondingly to regulate the quantity of gas supplied to the burner. Devices of the so-called "Venturi" type for controlling the flow-rate of the gas in dependence on the flow-rate of water are known for this purpose. These devices provide for a reduced cross-section to be inserted in the water supply line so as to generate a differential pressure which acts on the actuator of a valve for regulating the flow-rate of the gas in dependence on the flow-rate of water. In particular, the actuator is constituted by a diaphragm which is subjected to the differential pressure and is connected mechanically by means of a system of rods to the closure element of the valve regulating the flow-rate of gas by means of a system of rods . However, these devices bring many disadvantages, amongst which is poor efficiency in regulating the flow-rate of the fuel gas, which causes the temperature of the water supplied to vary, also considerably, with variations in its flow-rate. A further disadvantage is that these devices involve an insecure separation between the water and gas circuits, resulting in possible infiltrations and, in any case, complexity of the sealing systems. Disclosure of the invention The problem upon which the present invention is based is that of providing a valve unit for regulating the flow-rate of fuel gas in dependence on the flow-rate of water, particularly for water-heaters, which is designed structurally and functionally to overcome the limitations described above with reference to the prior art mentioned. This problem is solved by the present invention by means of a valve unit formed in accordance with the following claims . Brief description of drawings The characteristics and the advantages of the invention will become clearer from the detailed description of a preferred embodiment thereof, described by way of non- limiting example with reference to the appended drawings, in which: - Figure 1 is a front view showing, in section, a valve unit formed in accordance with the present invention, - Figure 2 is a view of the valve unit, sectioned in the plane II-II of Figure 1. Best mode for carrying out the invention In the drawings, a valve unit for regulating the flow- rate of a fuel gas in dependence on a flow-rate of water, formed in accordance with the present invention, is generally indicated 1. The valve unit 1 comprises a hydraulic turbine 2 the rotor 2a of which is housed in a chamber 3 and supported rotatably for rotating about an axis X. Inlet and outlet openings indicated 4 and 5 respectively, are provided in the chamber 3 for the connection of the turbine 2 in a line through which the water to be supplied flows. The openings 4 and 5 are arranged in a manner such that the rotor 2a of the turbine 2 is rotated about the axis X by the flow of water. It is intended that the turbine may be driven by the entire flow of water treated or by a known fraction thereof . An eddy-current brake, generally indicated 6, is associated with the turbine 2 and comprises an annular body 7 made of electrically conductive material, preferably aluminium or copper, extending coaxially from only one side 2b of the rotor 2a and a magnetic field generator such as a permanent magnet 9, coaxial with the annular body 7 and also supported rotatably in the valve unit 1 for rotating about the axis X. The annular body 7 and the permanent magnet 9 are housed, respectively, in a first chamber 8 formed in the chamber 3 and in a second, hydraulically separate chamber 10 which thus communicates neither with the chamber 3 nor with the first chamber 8. The first chamber 8 preferably extends coaxially around the second chamber 10 housing the permanent magnet 9, so that the wall separating the chambers is thin. The valve unit 1 also comprises a regulation valve 11 inserted in a duct 12 through which the fuel gas flows, for modulating the flow-rate thereof. The valve 11 includes a closure element 13 mounted on one end of a rod 14 which in turn is connected to the permanent magnet 9 by transmission actuator means 15. The actuator means 15 are of the type with gears and comprise a pinion or sprocket 16 keyed to a shaft 16a extending axially from the magnet 9. The pinion 16 is meshed with a rack 17 formed on the rod 14. According to a preferred embodiment, the rod 14 is disposed along an axis Y substantially perpendicular to the axis X of the pinion 16 and the rack 17 is constituted by teeth extending peripherally around the rod 14. By virtue of the action of the eddy-current brake, the closure element 13 is movable along the axis Y between a closure position, in which it is in abutment with a respective seat 19 to prevent the flow of gas along the duct 12, and an open position in which it is removed from the seat 19. This movement is opposed by a spring 20 a first end of which is in abutment with a shoulder 13a formed on the closure element 13 so as to urge the closure element 13 against the seat 19. The valve unit 1 performs its function of controlling the flow-rate of the fuel gas in dependence on the flow-rate of water in the terms indicated briefly below. For each value of the flow-rate of the water in the chamber 3, there is a corresponding value of the rate of rotation of the turbine 2. The eddy-current brake 6 transforms this rate of rotation into a corresponding torque which is transmitted to the rod 14 of the regulation valve 11 by the permanent magnet 9 and the actuator means 15. This action of the eddy-current brake is regulated owing to the fact that, in a conductor which is subjected to a variation in magnetic induction flux, electrical currents are created which tend to oppose the variation in flux. In the specific case, the rotary motion of the annular body 7 about the permanent magnet 9 creates, in the body 7, induced currents the electromagnetic field of which opposes this relative motion, tending to "drag" the magnet 9 along with it. The greater is the rate of rotation of the rotor 2a and hence of the annular body 7 fixed thereto, the greater will be the force with which these induced currents will tend to drag the permanent magnet 9 along in this rotary motion, thus generating the above-mentioned torque. As a result of the torque, the closure element 13 is moved along the axis Y in opposition to the spring 20, away from the seat 19, allowing the gas to flow. The position reached by the closure element 13 is defined by the equilibrium between the resilient force of the spring 20 tending to close the closure element 13 and the torque generated by the eddy-current brake. Clearly, the greater is the torque generated by the brake, the greater is the degree of opening of the closure element 13 and hence the greater is the flow-rate of fuel gas. It is clear from the remarks set out above that, for every value of the flow-rate of water, there is a corresponding rate of rotation of the rotor 2a, a corresponding torque transmitted by the eddy-current brake 6, a corresponding movement of the closure element 13 and, finally, a corresponding value of the flow-rate of fuel gas. In the preferred embodiment described herein, the valve unit 1 is intended to be fitted on an instantaneous water- heater with a pilot flame . The valve unit is therefore also provided with a thermoelectric valve 21 for shutting off the fuel-gas duct 12, with actuator means 22 for manual opening of the thermoelectric valve, and with an auxiliary pilot- flame supply duct which is not shown in the drawings but which branches off the duct 12 in a position between the thermoelectric valve and the regulation valve . The thermoelectric valve 21 is disposed upstream of the regulation valve 11 and preferably in a position substantially parallel thereto. The functional characteristics of the thermoelectric valve 21 provide, in conventional manner, for a capability of its closure element 23 to be held in a position in which the fuel gas circuit is open by means of an internal electromagnetic circuit controlled by a pilot-flame presence indicator, for example, a thermocouple . Should the pilot flame go out, the closure element 23, which would no longer be held by the electromagnetic circuit, would be moved to the closure position by resilient means 24 so as to shut off the duct 12 for supplying the fuel gas to the burner of the water-heater. The actuator means 22 for manual opening of the thermoelectric valve 21 comprise a push-button 25 which is disposed outside the valve unit 1 and to which first and second parallel pressure elements, extending inside the valve unit and indicated 26 and 27, are fixed. The first pressure element 26 is arranged as an extension of the closure element 23 of the thermoelectric valve, and the free end of the second pressure element 27 is in abutment with the end of the spring 20 remote from the closure element 13 of the regulation valve. To enable the pilot flame to be supplied, the pushbutton 25 is pressed against the valve unit, thus moving the closure element 23 partially into the electromagnetic circuit of the thermoelectric valve, by means of the first pressure element 26. In this position, the fuel gas can flow to the auxiliary duct in order to supply the pilot flame without, however, being able to reach the burner through the regulation valve 11. The closure element 13 is in fact closed against the seat 19 by the spring 20 which, during this operation to move the push-button 25 is further compressed by the second pressure element 27. Lighting of the pilot flame operates the electromagnetic circuit of the thermoelectric valve which holds the closure element 23 in the open position without the need for operation of the actuator means 22, which can be released. These actuator means are returned to a position remote from the valve unit 1 by the action of the spring 20. The present invention thus overcomes the limitations described above with reference to the prior art mentioned, at the same time offering many advantages. A first advantage is constituted by the complete and total hydraulic separation between the water and gas circuits. Another advantage consists of the true proportionality of the regulation of the gas in dependence on the flow-rate of water and, not least, it should be borne in mind that the regulation is ensured by inexpensive operating means which are reliable over time.

Claims: Claims 1. A valve unit (1) for regulating the flow-rate of fuel gas in dependence on the flow-rate of water, particularly for water-heaters, comprising a valve (11) for regulating the flow-rate of the fuel gas and a turbine (2) including a rotor (2a) the rate of rotation of which is associated with the flow-rate of water, characterized in that the turbine (2) is connected to the valve (11) in order to regulate the flow- rate of the fuel gas in dependence on the flow-rate of water supplied to the turbine (2) . 2. A valve unit according to Claim 1, in which an eddy- current brake (6) is interposed between the turbine (2) and the valve (11) in order to transform the rate of rotation of the rotor (2a) of the turbine (2) into a signal for controlling the movement of a closure element (13) of the valve (11) . 3. A valve unit according to Claim 2 , in which actuator means (15) are provided for the closure element (13) and the eddy-current brake (6) is connected to the actuator means (15) for the operative control thereof. 4. A valve unit according to Claim 3 , in which the closure element (13) is movable with continuous adjustment under the action of the actuator means (15) . 5. A valve unit according to Claim 3 or Claim 4 , in which resilient means (20) are provided and act on the closure element (13) in opposition to the actuator means (15) . 6. A valve unit according to one or more of Claims 2 to 5, in which the eddy-current brake (6) comprises a magnetic field generator (9) fixed for rotation with one of the actuator means (15) and the rotor (2a) of the turbine (2) and a conductor element (7) fixed for rotation with the other of the actuator means (15) and the rotor (2a) of the turbine (2) , the magnetic field generator (9) being associated with the conductor element (7) so that the flux of the magnetic field generated by the magnetic field generator (9) varies, with regard to the conductor element (7) , when the rotor (2a) is rotated in the turbine (2) . 7. A valve unit according to Claim 6, in which the conductor element (7) is made of a metal with a low coefficient of resistivity. 8. A valve unit according to Claim 7, in which the conductor element (7) is made of aluminium or copper. 9. A unit according to any one of Claims 6 to 8 , in which the magnetic field generator (9) is a permanent magnet. 10. A unit according to any one of Claims 6 to 9, in which the conductor element comprises an annular body (7) extending coaxially from the rotor (2a) , the annular body (7) being housed in a first chamber (8) of the valve unit (1) , the magnetic field generator (9) being housed in a second chamber (10) of the valve unit (1) , the chambers (8, 10) being hydraulically separate from one another. 11. A unit according to Claim 10, in which the first chamber (8) extends coaxially around the second chamber (10) . 12. A valve unit according to one or more of Claims 6 to 11, in which the actuator means (15) comprise a shaft (16a) extending from the magnetic field generator (9) , a pinion (16) keyed to the shaft (16a) , and a rack (17) meshing with the pinion (16) and connected to the closure element (13) . 13. A valve unit according to Claim 12 , in which the rack (17) has teeth extending peripherally around a rod (14) on one end of which the closure element (13) is mounted. 14. A valve unit according to one of more of Claims 2 to 13, comprising a thermoelectric valve (21) for shutting off the fuel gas and actuator means (22) for manual opening of the thermoelectric valve (21) , the actuator means (22) comprising a pair of pressure elements (26, 27) which are operated simultaneously and act, respectively, on the closure element (13) in order to bring about closure thereof, and on the thermoelectric valve (21) , in order to bring about opening thereof .

Inventors: BORTOLIERO MICHELE, GALLOCCHIO VANNI, GRANDO MAURIZIO, BORTOLIERO, MICHELE, GALLOCCHIO, VANNI, GRANDO, MAURIZIO
Applicants: BORTOLIERO MICHELE, GALLOCCHIO VANNI, GRANDO MAURIZIO, OP CONTROLS S P A, BORTOLIERO, MICHELE, GALLOCCHIO, VANNI, GRANDO, MAURIZIO, OP CONTROLS S.P.A.
Application year: 2000
Main classification: F23N1
IPC codes: F23N1