Device for the Multifunctional Control of the Supply of a Combustible Gas to a Burner Apparatus

Abstract

A device for the multifunctional control of the supply of a combustible gas to a burner apparatus is disclosed and comprises, in a main gas supply duct, an electromagnetically controlled electrovalve with an on/off function, a flow regulator downstream of this electrovalve and comprising a valve seat, a respective shutter associated therewith and controlled by a reversible electric motor, such as a step-by-step motor, for the control of the displacement of the shutter with respect to the valve seat. In the device the intercepted condition of the valve seat is detected and a signal correlated with the detected intercepted condition of the valve seat is generated this signal being adapted to supply the corresponding consent for the control to open or close the electrovalve, in order to enable or prevent the passage of gas through this duct in the phases of ignition and extinction of the burner respectively.

Description

TECHNICAL FIELD

The present invention relates to a device for the multifunctional control of the supply of a combustible gas to a burner apparatus.

TECHNOLOGICAL BACKGROUND

The invention is of particular, but not exclusive, application in the sector of devices for the multifunctional control of the supply of combustible gases to valve units adapted for uses in heating appliances such as stoves and fires, whose regular operation needs to be ensured even when there is no mains electricity supply for a period of time.

A first known solution entails, in the above-mentioned applications, the use of thermoelectrically actuated supply valve units, in which a manual setter and automatic operation by means of a permanent-flame pilot burner are typically provided. The drawbacks of such a solution lie in particular in the need for a manual setter and in the need for a permanent pilot burner entailing substantial energy consumption. There is, however, the advantage that operation is ensured even in the case of a power cut in the electricity mains.

A second type of known device entails the use of so-called automatic valve units, supplied by the electricity mains. While these ensure automatic operation and do not require a permanent-flame pilot burner, they suffer from the drawback that their operation is discontinued in the case of an electricity power cut.

In both types of solution, at least one pair of electrovalves, preferably disposed in series in the gas path, is typically provided in order to ensure appropriately secure operation (complying, moreover, with the technical safety standards in force), but entails substantial energy consumption, an aspect which conflicts with the requirements encountered in the particular applications discussed above, i.e. in which it is wished to ensure correct operation even in the case of temporary power cuts in the electricity mains.

Solutions to these problems have been proposed, including in devices produced by the Applicants, in which a valve seat with a shutter controlled by an operator of proportional type, such as a step-by-step electric motor, supplemented by a diaphragm pressure regulator, is provided as an alternative to one of the two electrovalves. In this case, the provision of such a modulator device integrating both the modulation and the closure functions offers the advantage of low energy consumption. Energy is in practice consumed only during the phase of transition from one modulation to the next (the time in which the motor is actuated) as no standby power is required, in contrast to the case of a conventional electromagnet which has to be supplied permanently. The drawback of this solution lies in the fact that it does not ensure automatic closure of the seat controlled by the shutter by means of the step-by-step motor when the electrical supply is discontinued, in contrast to what happens with the use of a resiliently recalled electromagnetic operator in an electrovalve of conventional type.

DISCLOSURE OF THE INVENTION

The main object of the invention is to provide a multifunctional device which ensures appropriately safe closure if the electrical supply is discontinued, on a par with that which can be obtained with a pair of electrovalves in series with one another, but which entails the use of operators, for the control of the modulating shutter, with low energy consumption, so as to ensure operation for an appropriate period of time even in the case of a power cut in the mains electricity supply by means of the use of simple energy accumulators such as, for instance, batteries of traditional type.

These and other objects to be set out below are achieved by a device for the multifunctional control of the supply of a combustible gas to a burner apparatus embodied in accordance with the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristic features and advantages of the invention are set out in detail in the following description of some preferred embodiments, given purely by way of non-limiting example, made with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic view of a device of the present invention;

FIG. 2 is a diagrammatic view in longitudinal section of a detail of FIG. 1;

FIG. 3 is a diagrammatic view in longitudinal section of a variant of the detail of FIG. 2;

FIG. 4 is a diagrammatic view in partial longitudinal section of a first variant of the device of FIG. 1;

FIG. 5 is a diagrammatic view in partial longitudinal section of a further variant of the invention.

PREFERRED EMBODIMENTS OF THE INVENTION

In FIG. 1, a device for the multifunctional control of the supply of a combustible gas to a burner apparatus, for instance a fire or like consumer unit, embodied in accordance with the present invention, is shown overall by 1.

The device 1 comprises a valve unit disposed in a main gas supply duct 2 between a gas inlet zone 3 and an outlet zone 4 where the gas is supplied to a main burner 5.

The valve unit comprises an electrovalve 6, known per se, disposed in the duct 2 to the rear of the inlet zone, adapted to enable or safety to intercept the passage of gas in the duct 2 by means of an on/off control of the shutter with respect to the corresponding valve seat. It is, for instance, of the type which is normally closed and comprises an electromagnetic actuator, known per se, directly controlling the shutter with a resilient recall adapted to displace the shutter to close the valve seat when the electromagnet is not supplied.

Downstream of the electrovalve 6, a pilot duct 7 starts from the main duct 2 and is adapted to supply a pilot burner 8 associated with the main burner in a conventional manner. A regulator, in which a pressure regulator with diaphragm control is integrated, shown overall by 9, is further disposed in the duct 2, downstream of the duct branch 7. A gas supply pressure modulator device is provided in the regulator 9. This device is of the type disclosed in the prior International Application PCT/IT2004/000020 in the name of the Applicants, whose description is understood to be incorporated here in respect of any detail not explicitly described. FIGS. 2 and 3 show two embodiments of this regulator, but only the variant of FIG. 2 will be briefly described below for greater clarity of description. It will be appreciated that the variant of FIG. 3, in which details similar to those of FIG. 2 bear the same reference numerals, may also be provided in the device of the present invention.

The regulator 9 comprises a valve seat 10, provided in the duct 2, cooperating with a shutter 11 whose control rod 12 is rigidly connected to a control diaphragm 13. The diaphragm 13 is subject on one side to the gas supply pressure and on the other side to a resilient load generated by a spring 14 whose axial ends 14a, 14b are respectively connected to the diaphragm 13 and to a wall 15 of a stationary structure of the valve unit. The surface of the diaphragm 13 on which the spring 14 acts is also subject to atmospheric pressure as a result of the provision of an opening 16 through which the chamber housing the spring 14, bounded in part by the diaphragm 13 and by the wall 15, communicates with atmosphere.

The regulator 9 further comprises a rod-like member 17 which may be displaced in translation coaxially with the rod 12, which bears, at one end, a plate 18 disposed in a position facing the shutter 11. A spring between the plate 18 and the shutter 11 is shown by 19. An electric motor 20 is provided to control the shutter 11, which motor may for instance be, but is not necessarily, of the step-by-step type operationally connected to the rod-like member 17 to control the shutter 11 to perform a controlled movement with respect to the valve seat 10. The motor 20 is advantageously embodied as a step-by-step motor of the reversible type with means (for instance screw-nut or like couplings) for converting the rotation of the rotor into a movement of axial translation of the rod-like member 17 in which the positions reached by the latter in the axial direction are correlated with the number of revolutions of the motor. When the motor 20 is actuated, the member 17 is displaced from and towards the shutter so that the resilient load thereon generated by the spring 19 is gradually respectively decreased or increased and the pressure is therefore modulated proportionally in correlation with the ratio between the resultant of the resilient forces (springs 14 and 19) and the surface of the diaphragm 13 and the shutter 11 on which this resultant force acts.

A means for detecting the intercepted condition of the valve seat 10 is shown by 22. It preferably comprises a sensor of mechanical, electrical or optical type adapted to detect this condition and then to generate a signal S representative of this condition which is used to manage the operating phases of the device, as will be explained in detail below. This signal S is in particular supplied to a signal control and processing unit 24, shown only in outline, provided with circuit means 25 adapted to generate a consent signal C correlated with the signal S, this signal C being adapted to provide consent for the control to open or close the electrovalve 6 so as to prevent or enable the passage of gas through the latter, during the phases of ignition/extinction of the burner in accordance with the operating logic which will be explained in detail below.

The control unit 24 advantageously comprises an electronic circuit board of conventional type, such as those typically provided for the control of burner appliances, and is supplied by the electricity mains to provide, via transformer devices, the supply current to both the electrovalve 6, via a conductor line 26, and to the step-by-step motor 20, via a corresponding conductor line 27. The signal generated by flame detection means provided respectively on the main burner 5 and on the pilot burner 8 are also supplied to the circuit complex of the unit 24. These means comprise a flame sensor 28 on the pilot burner and a flame sensor 29 on the main burner.

According to a further characteristic feature of the invention, at least one buffer battery 30 is provided and is adapted to supply all the electrically supplied consumer units of the device 1, in particular the electromagnet of the electrovalve 6 and the motor 20, in the case of an electricity power cut which discontinues the supply of current from the mains. This battery 30, preferably of rechargeable type, is disposed in a remote position with respect to the main burner 5 and is preferably chosen to meet specifications able to ensure the correct electrical supply of the device for a predetermined period of time in the event of a power cut in the mains network.

In operation, the main stages of ignition can be summarised as the following sequence:

• • verification of closure of the shutter 11 on the seat 10 (signal C),
  • opening of the electrovalve 6 and ignition of the pilot burner 8,
  • detection of the presence of a flame at the pilot burner 8,
  • opening of the gas path to the main burner 5,
  • ignition of the main burner 5 by the pilot 8,
  • monitoring of the presence of a flame at the main burner by a sensor 29.

In normal operation, the flame level is then regulated to the pre-selected value in the main burner 5 by the modulation control actuated by the step-by-step motor 20. When it is wished to turn off the system, the relative stages can be summarised as the following sequence:

• • verification of closure of the valve seat 10 by actuation of the motor 20 by consent (signal S),
  • verification that the flame at the main burner 5 has been extinguished,
  • closure of the electrovalve 6,
  • verification that the flame at the pilot burner 8 has been extinguished.

If the above-mentioned condition of verification that the flame at the main burner 5 has been extinguished has not occurred within a predetermined time, a safety closure is provided with locking of the electrovalve 6 and signalling of a malfunction.

In the operating logic of the invention, in order to ensure that the valve seat 10 of the operator 9 has closed prior to the stage of ignition of the pilot 8, i.e. of the opening of the electrovalve 6 (which enables gas to pass into the pilot duct 7), this electrovalve is authorised to open by the consent signal C which is correlated with the signal S detected by the sensor 22 (adapted to detect the intercepted condition of the valve seat 10). Only when the signal S is representative of the intercepted condition of the seat 10, is the opening of the electrovalve 6 authorised. The correlation between the above-mentioned signals is also used at the extinction stage, when it is wished to close the electrovalve 6 at the end of the heating cycle, after the closure of the valve seat 10. The predetermined operating logic provides, moreover, that the opening consent mentioned above must always accord with the signal detected at the flame detection sensors 28 and 29 of the main burner 5 and the pilot burner 8.

This operating logic is justified as the choice of using, downstream of the electrovalve 6, a second valve with a relative shutter whose modulation and on/off closure is controlled by a step-by-step motor, is intended to achieve safe closure of this seat which is the same as or equivalent to that offered by a safety electrovalve (which closes when there is no voltage). To ensure this safe closure, bearing in mind that the step-by-step motor does not ensure automatic closure of the seat when there is no voltage, the shutter controlled by the motor is associated with a sensor adapted to determine the intercepted condition of the seat and to enable, by means of a consent signal, the opening of the gas path in the upstream electrovalve, subject to verification that the valve seat 10 has closed.

The use of the step-by-step motor to control the shutter 11 has, moreover, a number of advantages, the main advantage being that energy consumption is substantially lower than with an electromagnetic operator. In contrast to an electromagnet which has to be supplied permanently, the step-by-step motor does not require any standby power and consumes energy only during the stage of transition from one modulation level to another. This low energy consumption advantageously enables the use of a buffer battery of conventional type for the electrical supply of the overall device if there is a power cut in the electricity mains for a substantial period of time (even a few days), which cannot be achieved if the device, as in conventional solutions, comprises a pair of electrovalves which require standby powers which cannot really be ensured by a buffer battery of the above-mentioned type.

It is possible, moreover, further to reduce the energy consumption of the device by providing the electrovalve 6 with an electrical supply which accepts at least a double level of electrical power, in which a first larger power (of the order of a watt) is used as the power to raise the electromagnet (an extremely short event) and a second smaller power (of the order of some milliwatts) is sufficient to maintain the magnet (a permanent event), thus reducing the absorption of any buffer battery as far as possible. Operation of this type may be obtained either by supplying a single winding with two voltage levels or, preferably, by providing two separate windings, one of which is a high-resistance standby winding.

As an alternative to the electrovalve 6 of conventional type, a moving coil operator with a permanent magnet may also be provided, for instance of the type disclosed in International Application PCT/IT2004/000020.

The regulator 9 described above may be calibrated to a specific value as a function of the particular gas used. As an alternative, it is possible to provide for a single calibration for all the types of gas which may be used and to combine this with a specific adaptation of electrical type for each gas used.

This may be carried out by setting the number of steps of the motor 20 corresponding to the minimum and maximum rates of flow. This adaptation may be carried out mechanically or electronically, and in the latter case when the appliance is being manufactured (for instance by programming with a PC) or when it is being installed (on the control panel by the fitter).

The buffer battery 30 may be associated with a voltage conversion system to increase this voltage to the level required to drive the electronics and the flame detection. An indicator (possibly a threshold indicator) of the charge state of the battery may also be provided.

A remote control device to set the pre-selected flow, i.e. between the values of zero flow (appliance off), minimum flow and maximum flow and any flow value between the minimum and maximum values, may also be provided.

FIG. 4 shows a first variant of the device of the invention in which the electrovalve 6, rather than acting directly on the valve seat, is provided as a servo-valve, shown overall by 6a, with servo-assistance from an electromagnetic operator.

In further detail, a servo-circuit is provided in the main duct 2 and comprises a shutter 31 controlled by a diaphragm 32 associated with a respective main valve seat 33. The diaphragm 32 acts directly on the control rod of the shutter 31 which is in turn urged resiliently to close the seat 33 by a spring 34. One surface of the diaphragm 32 defines a pilot chamber 35 which communicates with the duct 2, upstream of the seat 33, by means of a pilot duct 36 bearing a throttle 37, and with the outlet 2a, downstream of the seat 33, by means of a throttle 37a of a duct 36a. The duct 36 can be selectively opened or closed by an electromagnet 38 of on/off type with resilient recall, acting on a shutter member 39 associated with the passage section of the duct 36 and which may be displaced from and towards a position intercepting this passage section.

In operation, with the electromagnet 38 excited as it is electrically supplied, the duct 36 enables the passage of gas and a pressure is generated in the pilot chamber 35, which pressure is correlated with the input pressure, as a function of the two throttles 37, 37a. In this way, the diaphragm 32, urged by the above-mentioned pressure force, tends to lift the shutter 31 from the seat 32 enabling gas to pass through the duct 2 in the direction of the pilot duct. Vice versa, when the electromagnet 38 is not excited, when there is no electrical supply to it, the interception of the pilot duct 36 causes the pressure in the chamber 35 to decrease and the resilient action of the spring 34, overcoming the action of the diaphragm, displaces the shutter 31 to close the seat 33 thereby intercepting the main gas path. It will be appreciated that the operating logic is the same as in the previous embodiment, direct control by the electrovalve 6 being replaced by indirect control by the servo-valve 6a. The use of the servo-valve advantageously makes it possible substantially to reduce energy consumption and the power required, since the electromagnet 38, precisely because it is used in a servo-circuit, requires less operating and standby power than the electrovalve 6 with a direct electromagnet. An advantageous result of this lower power requirement is that a less powerful and costly buffer battery 30 is needed for use in power cuts, or a battery which has the same characteristics and ensures a longer period of coverage.

In the embodiment of FIG. 4, the pressure regulator is also disposed in the servo-assisted circuit of the valve 6 in a position separate from the flow regulator controlled by the step-by-step motor downstream of the servo-valve.

In this respect, a diaphragm pressure regulator 40, known per se, is provided, wherein one diaphragm side defines a pilot chamber 41 communicating, via a duct 42, with a downstream section of the duct 2 and is also able to intercept the outlet section of an auxiliary duct 43 communicating with the pilot chamber 35 of the servo-valve. The opposite side of the diaphragm is urged by a calibration spring 44 disposed in a chamber open to atmosphere by means of an opening 45. The pressure regulator is designed to react to supply pressure variations in order to offset them and bring the pressure to a predetermined calibrated value by regulation of the spring 44.

FIG. 5 shows a further variant of the device of the invention, in which details similar to those of the preceding embodiment of FIG. 4 bear the same reference numerals.

This variant has slight differences with respect to the embodiment of FIG. 4, one of which lies in the fact that the control diaphragm 32 of the servo-valve 6a is disposed upstream of the valve seat 33 with respect to the direction of flow. Another slight difference lies in the fact that the pressure regulator, still disposed in the servo-circuit, comprises a separate shutter 50 associated with a valve seat 51 and bearing a shutter rod 53 coupled to the diaphragm 32. In operation, both the control to open and close the valve seat 33 by means of the electromagnet 38 in the servo-circuit and the regulation of the pressure by the servo-regulator 40, mirror the operating characteristics set out in respect of FIG. 4 to which reference should be made for further details.

In both embodiments of FIGS. 4 and 5, the main advantage connected with the use of the servo-valve 6a therefore lies in the smaller energy consumption required for the operation and standby of the corresponding electromagnet, which is reflected by the advantageous possibility of using lower-power batteries to ensure operation of the overall device in the case of a power cut in the electricity mains. Moreover, the provision of the pressure regulator by the servo-circuit offers better performance and also makes it possible to associate the step-by-step motor with a simple flow regulator formed solely by a shutter coupled to the corresponding valve seat and controlled by the motor.

The invention thus achieves the objects set out above and offers the above-described advantages in comparison with known solutions.

Claims

1. A device for the multifunctional control of the supply of a combustible gas to a burner apparatus, comprising, in a main gas supply duct:

an electromagnetically controlled electrovalve with an on/off function,

a flow regulator downstream of the electrovalve and comprising a valve seat, a respective shutter associated therewith and controlled by a reversible electric motor for the control of the displacement of the shutter with respect to the valve seat,

means for detecting the intercepted condition of the valve seat,

means for generating a signal correlated with the detected intercepted condition of the valve seat, said signal being adapted to supply the corresponding consent for the control to open or close the electrovalve, in order to enable or prevent the passage of gas through the duct in the phases of ignition and extinction of the burner respectively.

2. A device according to claim 1, wherein the means for detecting the intercepted condition of the valve seat associated with the shutter comprise sensor members of the mechanically, electrically or optically actuated type.

3. A device according to claim 1, comprising additional energy storage means adapted temporarily to supply said device, and in particular the electrovalve in the event of a power cut in the electricity mains.

4. A device according to claim 3, wherein the energy storage means comprise at least one buffer battery.

5. A device according to claim 4, wherein the buffer battery is of rechargeable type.

6. A device according to claim 4, wherein the buffer battery is located in a position remote from the burner apparatus.

7. A device according to claim 1, comprising respective means for detecting a flame at the main burner and at the pilot burner associated therewith.

8. A device according to claim 7, wherein means are provided for comparing the consent signal with the signal from the flame detection means at the main burner so as to enable the device to operate only if these signals accord, so as to ensure that there is no flame at the main burner with the electrovalve in the condition intercepting the gas passage and vice versa, i.e. there continues to be a flame with the electrovalve open.

9. A device according to claim 2, wherein the sensors of mechanical type comprise proximity sensors adapted to detect that the shutter has reached a position in its control stroke.

10. A device according to claim 2, wherein the means for detecting the intercepted condition of the valve seat comprise means for verifying that electrical current is circulating in the control circuits of the electrically supplied members of said device.

11. A device according to claim 1, comprising a pressure regulator integrated in the flow regulator and comprising a control diaphragm of the shutter acting on the actuator rod of the shutter so that the modulation and on/off functions are integrated in the regulator.

12. A device according to claim 1,, wherein the electrovalve comprises an electromagnetic operator acting directly on the corresponding valve seat.

13. A device according to claim 1, wherein the electrovalve comprises a servo-valve with an electromagnetic control operator.

14. A device according to claim 13, comprising a pressure regulator operationally associated with the servo-valve.

15. A device according to claim 13, wherein the servo-valve comprises a respective valve seat associated with a respective shutter with a diaphragm control, for the opening of the seat in opposition to a resilient recall, one side of the diaphragm being subject to a pilot pressure existing in a pilot chamber which communicates with the main duct via a pilot duct, the electromagnetic operator being adapted to act to close or open the pilot duct so as indirectly to control, via the diaphragm control, the respective shutter of the servo-valve.

16. A device according to claim 15, in which a second communication duct is provided between the pilot chamber of the servo-valve and a section of the main duct downstream of the servo-valve, the pressure regulator with diaphragm control being disposed in this the duct.

17. A device according to claim 2, comprising additional energy storage means adapted temporarily to supply said device, and in particular the electrovalve in the event of a power cut in the electricity mains.

18. A device according to claim 5, wherein the buffer battery is located in a position remote from the burner apparatus.

19. A device according to claim 14, wherein the servo-valve comprises a respective valve seat associated with a respective shutter with a diaphragm control, for the opening of the seat in opposition to a resilient recall, one side of the diaphragm being subject to a pilot pressure existing in a pilot chamber which communicates with the main duct via a pilot duct, the electromagnetic operator being adapted to act to close or open the pilot duct so as indirectly to control, via the diaphragm control, the respective shutter of the servo-valve.