WO2007060696A1

WO2007060696A1 - Device for controlling the delivery of a combustible gas to a burner apparatus

Info

Publication number: WO2007060696A1
Application number: PCT/IT2005/000686
Authority: WO
Inventors: Stefano Zanella; Gianpiero Turrin
Original assignee: Sit La Precisa S.P.A.
Priority date: 2005-11-23
Filing date: 2005-11-23
Publication date: 2007-05-31
Also published as: EP1952064A1; TW200720593A; CA2630767A1; US20080268388A1

Abstract

A device for controlling the delivery of a combustible gas to a burner apparatus comprises a main pipe (2) for delivery of the gas in which are disposed a first and a second servovalve (5, 6), respectively in cascade with each other, with respect to the direction of flow of the gas, the servovalves including respective valve seats (5a, 6a) associated with corresponding shut-off means (5b, 6b) with diaphragm control (5c, 6c) for the opening of the seats in opposition to respective resilient return means (5d, 6d), the first and second servovalve (7, 13) comprising a respective first and second control solenoid valve (7, 13) with electromagnetic operating means for controlling the opening/closure of the corresponding servovalve (5, 6), the solenoid valves being arranged to act for opening/closure of pipes of respective servo-assisted control circuits, so as to control indirectly, by way of the diaphragm control, the respective shut-off means (5b, 6b) of the corresponding servovalve (5, 6), the pipes of the control circuit placing the main pipe (2) in fluid communication with respective control chambers (10, 17) of the servovalves, one side of the diaphragms (5c, 6c) of said diaphragm controls being subjected to the pressure existing in the respective control chamber. The intake pipes (8, 9) of the respective control circuits, capable of picking up the pressure signal to be transmitted to the corresponding control chamber (10, 17), are both respectively connected, in fluid communication, with the main pipe (2), upstream of the first servovalve (5).

Description

Device for controlling the delivery of a combustible gas to a burner apparatus. Technical field

The present invention concerns a device for controlling the delivery of a combustible^' gas to a burner apparatus, according to the characteristics mentioned in the preamble of main claim 1. Technological background

The invention is placed particularly, but not exclusively, in the field of devices for the multi-functional control of the delivery of combustible gases in valve units arranged for use in heating apparatus such as stoves and fireplaces, in which there is a need to ensure the operation thereof also in the absence of the mains electrical supply for a certain period of time. In a typical known solution for such devices, provision is made for associating a magnetic thermocouple safety unit with a corresponding system with manual arming with a servovalve having an electromagnetic operating means for the control of a servo-assisted gas circuit (servo circuit), the electrical supply to which is guaranteed by the thermoelectricity generated by a thermopile heated in parallel with the thermocouple by the pilot burner. Such a solution, although it may have the advantage of ensuring independence from external electric power sources, still has the limitation of the need for manual arming.

In order to render the operation of such a device automatic it would be conceivable to substitute the magnetic safety unit with a solenoid valve with electromagnetic control. In such a configuration, however, the control electromagnet, operating on the respective valve which opens the full gas capacity, would absorb a high power and therefore would not lend itself well to being fed sufficiently by a battery, in the event of interruption of the main electrical supply, so as to ensure an adequate life of the battery itself. A further known solution, which would seem, at least in part, to remedy the aforesaid limitations, is to provide a pair of servo-assisted valves, disposed in series along the gas pathway, in which the safety valve (on/off type) is then also a servovalve with electromagnetic operating means for controlling the relevant servo circuit. In this configuration, since the solenoid valves with electromagnetic operating means and which control the assistance circuits to the servovalves, act to open/close reduced gas pathways (of the control circuit), the power absorbed thereby is rather modest and in any case much less than that of the known solutions previously mentioned, it being therefore possible in this case to conceive of the use of batteries having sufficient life for the supply in the event of a blackout of the main electrical supply. In this solution, however, since for regulating the operation (opening of the valve shut-off means) of each of the servo-valves it is in any case necessary that there should be a loss of load (pressure drop) between the sections upstream and downstream of the respective valves, such a configuration, in which the individual load losses add up, involves a double load loss which, by influencing the characteristic of the capacity delivered, may not prove to be tolerable and acceptable in normal applications. Description of the invention

The problem underlying the present invention is that of providing a device for controlling the delivery of a combustible gas to a burner apparatus, structurally and functionally designed so as to allow the limitations mentioned with reference to the prior art cited to be overcome.

This probieππ is solved by the invention by means of a device for controlling the delivery of a combustible gas to a burner apparatus produced according to the claims which follow. Brief description of the drawings

Further characteristics and advantages of the invention will become clearer from the following detailed description of some preferred exemplary embodiments thereof, illustrated by way of non-limiting example with reference to the appended drawings, in which:

Figure 1 is a view in longitudinal section of a first example of a device produced according to the present invention,

Figure 2 is a view in longitudinal section of a second example of the device according to the invention,

Figure 3 is a view in longitudinal section of a third example of a device according to the invention,

Figures 4 to 6 are diagrammatic views of the devices respectively of Figures 1 to, 3, - Figure 7 is a view corresponding to those in Figures 4 to 6 of a device according to the prior art,

Figures 8 and 9 are views respectively in longitudinal section and diagrammatic view of a fourth exemplary embodiment of the invention, - Figures 10 and 11 are views respectively in longitudinal section and diagrammatic view of a fifth exemplary embodiment of the invention, Figures 12 and 13 are views respectively in longitudinal section and diagrammatic view of a sixth exemplary embodiment of the invention, Figure 14 is a capacity/pressure diagram for the configurations of the devices of the preceding figures,

Figure 15 is a diagrammatic view of a further variant of the invention. Preferred ways of implementing the invention With initial reference to Figure 1, the reference 1 indicates as a whole a first example of a device for controlling the delivery of a combustible gas to a burner apparatus,- such as a fireplace or similar use, produced according to the present invention. The device 1 comprises a valve unit disposed in a main gas delivery pipe 2, between a gas inlet section 3 and an outlet section 4 where the gas is fed to a main burner, not shown in the drawing.

Along the main pipe 2 are disposed a first and a second servovalve, indicated as a whole respectively by 5 and 6, placed in cascade with each other such that the servovalve 6 is downstream of the servovalve 5, with respect to the direction of the flow of gas delivered through the pipe 2. Each servovalve 5, 6 comprises a respective servo circuit including a respective valve seat 5a, 6a associated with a corresponding and respective shut-off means 5b, 6b with diaphragm control 5c, 6c, for the opening of the seats 5a, 6a, in opposition to respective resilient return means, such as respective springs 5d, 6d.

The first servovalve 5 performs the function of on-off valve for the safety closure of the main gas pathway and is associated with a solenoid valve for controlling the servo assistance circuit, and indicated by 7, being placed for opening/closure of a control pipe 8 of the servo circuit, which constitutes the intake pipe for the pressure signal to be transmitted to the control chamber of the servo circuit, as will appear in detail in the continuation of the description. The diaphragm 5c acts directly on the control stem 5e of the shut-off means 5b, which is in its turn urged to close the seat by the spring 5d.

One side of the diaphragm 5c defines a control chamber 10, which communicates with the main pipe 2, upstream of the servovalve 5, by means of the control pipe 8. More particularly, in the pipe 8 there is identified a first portion 8a, communicating with the inlet section 3 and on which is disposed the solenoid valve 7, and a second portion 8b, in prolongation of the preceding portion, communicating with the chamber 10. At the solenoid valve 7, the relevant portion of pipe 8 is selectively opened or closed by means of an electromagnet 11, of the on-off type with resilient return, acting on a shut-off member 12 associated with the passage cross- section of the pipe 8 and displaceable from and towards a position for blocking the passage cross-section. The second portion 8b of the pipe 8 also communicates with a control pipe 9 of the second servovalve 6. More particularly, the pipe 9 comprises a first portion 9a communicating with the portion 8b and a second portion 9b, in prolongation of the first portion 9a, communicating with the respective control chamber 17 of the second servovalve. Between the portions 9a and 9b is disposed in the pipe 9 a second solenoid valve 13, arranged for the servo assistance control of the second servovalve 6.

At the solenoid valve 13, the relevant portion of pipe 9 is selectively opened or closed by means of an electromagnet 14, of the on-off type with resilient return, acting on a shut-off member 15 associated with the passage cross- section of the pipe 9 and displaceable from and towards a position for blocking the passage cross-section.

The pipe 9, together with the pipe portion 8 communicating therewith, performs the function of intake pipe for the pressure signal to be transmitted to the control chamber 17 of the respective servo circuit, the chamber 17 being defined on one side of the diaphragm 6c.

It should be noted that both the intake pipes 8, 9 of the respective control chambers 10, 17 are both connected, in fluid communication, with the main pipe 2, upstream of the first servovalve 5.

The reference 16 indicates an optional auxiliary pilot pipe which extends from the main pipe 2 at a section thereof lying between the valve seats 5a, 6a of the respective servovaives, the auxiliary pipe being arranged for supplying a pilot burner, not shown in the drawing.

The control chamber 10 is also connected with a section of the main pipe 2 lying between the valve seats 5a, 6a, by means of a pipe 8c, on which a constriction 20 is further provided. A second constriction arranged in the portion 9b of the control pipe 9 is indicated by 21.

The second control chamber 17 is connected with the outlet section 4 of the main pipe 2, downstream of the valve seat 6a of the second servovalve, by means of a respective discharge pipe 18, on which there may also be provided a pressure regulator, indicated as a whole by 22. This is a diaphragm pressure regulator, conventional in itself, in which one diaphragm side defines a control chamber 23 communicating, by means of a part 18a of the pipe 18, with the outlet section 4 of the main pipe 2 (downstream of the servovalve 6) and is also capable of blocking the outlet cross-section of the other part 18b of pipe 18 communicating with the control chamber 17. The opposite diaphragm side is urged by a calibrating spring 25 disposed in a chamber open to the atmosphere through an opening 26. The pressure regulator 22 is designed to react to the variations in delivery pressure and also to compensate for same and bring the pressure to a predetermined calibration value by means of adjustment of the spring 25.

In operation, with electromagnets 11, 14 de-energized, the intake pipes 8, 9 communicating with the control chambers are blocked (by the respective solenoid valves 7, 13) and the resilient return action of the spring 5d, 6d effects the closure of both the valve seats 5a, 6a of the respective servovalves. On a demand for lighting of the burner, firstly only the electromagnet 11 is energized, which by opening the pipe 8, permits the supply of gas to the pilot burner via the corresponding opening of the servovalve 5, which opening is controlled by the pressure picked up in the control chamber 10 by means of the intake pipe 8 (in portions 8a and 8b). In this step of lighting of the pilot burner, the intake pipe 9 communicating with the control chamber 17 is still blocked by the solenoid valve 13 (with respective electromagnet 14 de-energized), effecting the closure of the valve seat 6a.

Following the correct lighting of the pilot burner, the second electromagnet 14 is also energized, and consequently the portion 9b of the intake pipe 9 is opened to the passage of gas, and in the control chamber 17 a corresponding pressure is established, correlated with the inlet pressure, as a function of the constriction 21. In this way the diaphragm 6c, urged by the aforesaid pressure force, tends to lift the respective shut-off means 6b from the corresponding seat 6a, allowing the passage of gas through the main pipe 2, towards the main burner. The delivery pressure is further regulated by means of the diaphragm pressure regulator 22.

It should be noted that it is possible, owing to the fact that the control pressure of both the valves 5 and 6 is picked up in a section of the main pipe upstream of the first servovalve 5, to provide for a drop in pressure between the sections 3 and 4 of the main pipe 2 substantially equal to that necessary for opening a single servovalve correctly. In this way, with a single drop in pressure, the opening of both the servovalves 5 and 6 is obtained. Alternatively it is possible, with parity of closing forces acting on the shut-off means of the valves 5, 6, to provide servo control diaphragms having more restricted dimensions, with more reduced overall measurements.

For greater clarity, Figures 4 and 7 respectively show diagrammatically the operating circuits -of the device according to the aforesaid example of the invention and of a device according to the prior art.

In Figure 7, in which the same reference numbers are used as in the example described, the servovalves 5 and 6 are connected in series with each other and each respective solenoid valve 7, 13 is associated with the corresponding servo circuit. Indicated by A, A' are the sections upstream and downstream of the servovalve 5, while B', B indicate the sections upstream and downstream of the servovalve 6. The known system provides for a first loss of load between A and A¹, having a value such as to allow the correct opening ofthe first servovalve, and a second loss of load between B¹ and B for the correct opening of the- second solenoid valve. Such load losses, adding to each other along the main pipe, . influence the Capacity/Pressure characteristic, shown diagrammatically in Figure 4 by dashed lines. Conversely, by means of the control of the servovalves 5, 6, according to the present invention, it is possible to limit to a single loss of load the pressure drop between the section A and B, respectively upstream of the valve 5 and downstream of the valve 6, thus obtaining the correct operation of opening of both the servovalves by means of a loss of load having a value corresponding to that provided for the opening of each of the valves of the known systems.

It shouid further be noted that each of the solenoid valves 7, 13 may also be arranged to act in controlling the opening/closure of a second shut-off means (associated with the respective first shut-off means 12, 15) acting on a respective discharge pipe. The discharge pipe is extended to by-pass the respective constriction (of the control circuit) until it reaches a section downstream of the corresponding servovalve and is provided to allow rapid discharge of the flow of gas from the corresponding control chamber when the first shut-off means of the solenoid valve is in the blocking position. The aforesaid characteristic of the double shut-off means for each solenoid valve may optionally be provided in each of the variants of the invention, described in detail hereinafter. With reference to Figures 2 and 5, the reference Ia indicates as a whole a second example of a deyice according to the invention, in which details analogous to those of the preceding example are designated by the same reference numbers. Analogously to the preceding example, the control solenoid valves 7 and 13 of the respective servovalves 5 and 6 are disposed in cascade with each other along the portion 8a of the intake pipe 8, communicating with the pipe 2 upstream of the first valve 5. In this case, however, the portion 8d extends, with fluid connection, between the control chamber 10 and a section of the pipe 9 downstream of the second solenoid valve 13. Furthermore, the discharge pipe 8c of the chamber 10 extends between the latter and a section of the main pipe 2 downstream of the second servovalve 6. More particularly, the pipe 8c communicates with the portion 18a of the discharge pipe 18 of the second control chamber. The result is that the two control pipes of the servovalves are fed in parallel by means of the arrangement in series of the solenoid valves 7 and 13.

The pilot pipe 16 is provided, in this example, so that it extends from a section of the pipe 8 lying between the solenoid valves 7 and 13 (upstream of 13 and downstream of 7).

In operation, the opening of the first solenoid valve 7 entails the passage of gas through the pilot pipe 16, with both the valves 5 and 6 being blocked. Only by means of actuation for opening of the second solenoid valve 13, with the passage of gas into the portions 8b and 9b, is there the concomitant opening of the valves 5 and 6.

With reference to Figures 3 and 6, the reference Ib indicates as a whole a third example of a device according to the invention, in which details analogous to those of the preceding examples are designated by the same reference numbers. The device Ib differs principally from the device 1 in that the intake pipes 8 and 9 are independent of each other. In particular, the portions 8a and 9a of the respective control pipes, extending upstream of the corresponding solenoid valves 7 and 13, are directly connected to the main pipe upstream of the first servovalve 5. In this example, by means of opening of the solenoid valve 7 (with the solenoid valve 13 closed), with the passage of gas into the pipe 8 as far as the chamber 10, gas is fed exclusively to the pilot burner. Only by means of the subsequent further opening of the solenoid valve 13, with the passage of gas into the control pipe 9 as far as the chamber 17, is the control for opening the second valve 6 obtained with gas being fed to the main burner along the main pipe 2.

With reference to Figures 8 and 9, the reference Ic indicates as a whole a fourth example of a device according to the invention, in which details analogous to those of the preceding examples are designated by the same reference numbers. The device Ic, analogously to the device Ib, has the intake pipes 8 and 9 for the pressure signal for the respective control circuits, structurally independent of each other and communicating directly with a section of the main pipe 2 upstream of the first servovalve 5. The device differs, however, in that it provides for the pilot pipe 16 communicating, at one end thereof, with the control chamber 10, the passage cross-section for the gas at that end being blocked by the shut-off member of the first control solenoid valve 7.

The constrictions 20 and 21, in this example, are respectively provided along the pipes 8 and 9.

The second solenoid valve 13 is further arranged to block the end of the pipe 18 communicating with the control chamber 17. With reference to Figures 10 and 11, the reference Id indicates as a whole a fifth example of a device according to the invention, in which details analogous to those of the preceding examples are designated by the same reference numbers. The device Id differs from the device Ic principally in that the second solenoid valve 13 is arranged to block selectively the end of the control pipe 9 at the section communicating with the control chamber 17. As may be noted, in this example also, the intake pipes 8 and 9 of the control circuits for controlling the corresponding servovalves are independent of each other and are both connected directly to the main pipe upstream of the valve seat of the first servovalve 5.

With reference to Figures 12 and 13, the reference Ie indicates as a whole a sixth example of a device according to the invention, in which details analogous to those of the preceding examples are designated by the same reference numbers. This example differs principally from the device Ic in that the first solenoid valve 7 is arranged to block, selectively the end of the control pipe 8 at the section communicating with the control chamber 10. Furthermore, the constriction 21 is provided in the intake pipe 9 of the second control circuit, while the constriction 20 is provided in the intake pipe 8.

As may be noted, in this example also, the intake pipes 8 and 9 of the control circuits of the corresponding servovalves are independent of each other and are both connected directly to the main pipe upstream of the valve seat 5a of the first servovalve 5.

With reference to Figure 15, according to a further variant of the invention, applicable to each of the examples described above, provision is made for the pressure regulator also to perform the function of pressure modulator. To this end, provision may be made for the shut-off means of the regulator to be controlled by an electromagnetic operating means (for example an electromagnet) or by a reversible electric motor (for example of the stepping type), being able in both cases to provide for an electrical supply from the mains or by means of a battery.

Provision may also be made for controlling the opening/closure of the valve seat associated with one or both of the solenoid valves 7 and 13, by means of a part of the operating stroke of the control stem of the pressure modulator, actuated by the respective motor. Figure 15 illustrates, by way of example, an operating diagram for a version of the device according to the invention in which the control solenoid valve 13 is not provided, and the servovalve 6 is controlled by the same device which is provided for controlling the modulation of the capacity at the burner. In this variant, a stepping motor may for example be provided, in which the rotational motion of the rotor is conveniently transformed into a translational motion of an actuating stem acting on the spring 25 of the regulator. Alternatively, it is possible to provide for the use of an operating means with electromagnets, the movable part of which acts on the return spring 25. In this second case, provision may be made for the pressure value to increase proportionally with the electric current with which the electromagnet is supplied or, conversely, for the pressure to decrease proportionally with the current, this latter version being preferred owing to the fact that, in the absence of the mains, it is possible to limit the contribution of the optional reserve battery by not supplying the modulating electromagnet and causing the device to operate always at maximum (on- off function). In addition, when a reserve battery is provided, in order to guarantee operation in the absence of the mains electrical supply, the operation may be designed as "permanent pilot" operation instead of "intermittent pilot", for reasons of energy saving in the actuation of the electromagnetic operating means. The invention solves the problem and achieves the aims proposed with the advantages mentioned with respect to the known solutions.

Claims

C L A I M S

1. A device for controlling the delivery of a combustible gas to a burner apparatus, comprising a main pipe (2) for delivery of the gas in which are disposed a first and a second servovalve (5, 6), respectively in cascade with each other, with respect to the direction of flow of the gas, said servovalves including respective valve seats (5a, 6a) associated with corresponding shut-off means (5b, 6b) with diaphragm control (5c, 6c) for the opening of said seats in opposition to respective resilient return means (5d, 6d), said first and second servovalve (5, 6) comprising a respective first and second control solenoid valve (7, 13) with electromagnetic operating means for controlling the opening/closure of the corresponding servovalve (5, 6), said solenoid valves being arranged to act for opening/closing pipes of respective servo- assisted control circuits, so as to control indirectly, by way of the diaphragm control, the respective shut-off means (5b, 6b) of the corresponding servovalve (5, 6), the pipes of the control circuit placing the main pipe (2) in fluid communication with respective control chambers (10, 17) of the servovalves, one side of the diaphragms (5c, 6c) of said diaphragm controls being subjected to the pressure existing in the respective control chamber, characterized in that the intake pipes (8, 9) of the respective control circuits, capable of picking up the pressure signal to be transmitted to the corresponding control chamber (10, 17), are both respectively connected, in fluid communication, with the main pipe (2), upstream of the first servovalve (5).

2. A device according to claim 1, wherein the control circuit of the first servovalve (5) comprises a first discharge pipe (8c) of the corresponding first control chamber (10) which is connected, in fluid communication, with a section of the main pipe (2) lying between the valve seats (5a, 6a) of the respective servovalves (5, 6).

3. A device, according to claim 1 or 2, wherein from the portion of main pipe (2) extending between the valve seats (5a, 6a) of the respective servovalves (5, 6) there extends a pilot pipe (16) for supplying gas to a pilot burner. 4. A device according to any one of the preceding claims, wherein said solenoid valves (7, 13) are disposed in cascade with each other, along a first common portion (8a) of intake pipe connected at one end thereof with a section of the main pipe (2) upstream of the first servovalve (5). 5. A device -according to claim 4, wherein a second portion (8b) of the intake pipe, capable of connecting the first control chamber (10) with the main pipe (2), extends between a section of said first common portion (8a) of intake pipe, lying between said control solenoid valves (7, 13), and the first control chamber (10). 6. A device according to claim 1, wherein the control circuits of the first and second servovalve comprise a respective first (8c) and second (18b) discharge pipe of the corresponding first (10) and second (17) control chamber, which are connected, in fluid communication, with a section of the main pipe (2) downstream of the second servovalve (6).

?. A device according to claim 6, wherein said solenoid valves (7, 13) are disposed in cascade with each other, along a first common portion (8a) of intake pipe connected at one end thereof with a section of the main pipe (2) upstream of the first servovalve (5).

8. A device according to claim 7, wherein from said first common portion (8a) of intake pipe there extends, at a section lying between said control solenoid valves (7, 13), a pilot pipe (16) for supplying gas to a pilot burner.

9. A device according to one or more of the preceding claims, comprising a pressure regulator (22) with diaphragm control disposed In the portion of pipe of the control circuit of the second servovalve (6), which extends between the corresponding control chamber (17) of said second servovalve (6) and a section of the main pipe (2) downstream of the second servovalve (6).

10. A device according to claim 9, wherein said pressure regulator (22) comprises actuating means operationally connected to the shut-off means of said regulator for controlling in modulation the displacement of said shut-off means and consequently modulating the pressure controlled by said regulator.

11. A device according to claim 10, wherein an electromagnetic operating means is provided for controlling said actuating means. 12. A device according to claim 11, wherein a reversible electric motor, of the stepping type, is provided for controlling the displacement of the shut-off means of said diaphragm pressure regulator (22).