Note: Descriptions are shown in the official language in which they were submitted.
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Device for the multifunctional control of the supply of a combustible gas to a
burner apparatus
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
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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
s 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
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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
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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.
1s 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
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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,
5 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
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
20 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
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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
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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-
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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
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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
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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
5 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
10 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
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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.
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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.
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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
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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
s 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.
