Note: Descriptions are shown in the official language in which they were submitted.
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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
io 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
ls 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
20 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
25 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 sufficie'ntly by a battery, in the event of interruption of the
main
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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 limitatioris, 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
io 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
zo 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
z.s mentioned with reference to the prior art cited to be overcome.
T iiiS jJi'vuiei i i5 st5iveu uy r-he invention by means oT a device for
controiling
the delivery of a combustible gas to a burner apparatus produced according
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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
io 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
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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
io 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
is 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
20 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
25 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
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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.
5 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.
io 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
is 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-
20 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
25 chamber 17 being defined on one side of the diaphragrri 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
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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 servovalves, 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 vafve 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
io 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.
is 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
20 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
25 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
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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
io 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
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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
io 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 A', having a value such as to allow the
correct opening ofthe first servovalve, and a second loss of load between B'
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 should 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
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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 la 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.
T he 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
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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,
5 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 lb 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
io reference numbers. The device lb differs principally from the device 1 in
that the intake pipes 8 and 9 are independerit 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.
is 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 1c 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
zs reference numbers. The device 1c, analogously to the device 1b, has the
intake pipes 8 and 9 for the pressure signal for the respective control
circuits, structurally independent of each other and communicating directly
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with a section of the main pipe 2 upstream of the first servovalve S. 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 1d differs from the device 1c 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 le 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 1c in that the first solenoid
valve 7 is arranged to biock, selectively the end of the control pipe 8 at the
section communicating with the control chamber 10.
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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
io 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
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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).
io 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.
