U.S. patent application number 13/326100 was filed with the patent office on 2012-06-28 for device for controlling the supply of fuel gas to a burner , in particular for water heater appliances.
This patent application is currently assigned to SIT LA PRECISA S.P.A. CON SOCIO UNICO. Invention is credited to Gianpiero TURRIN.
Application Number | 20120160186 13/326100 |
Document ID | / |
Family ID | 43737202 |
Filed Date | 2012-06-28 |
United States Patent
Application |
20120160186 |
Kind Code |
A1 |
TURRIN; Gianpiero |
June 28, 2012 |
DEVICE FOR CONTROLLING THE SUPPLY OF FUEL GAS TO A BURNER , IN
PARTICULAR FOR WATER HEATER APPLIANCES
Abstract
A device for controlling a gas supply to a burner includes a
main duct, which is provided with at least one main valve including
a valve seat and associated shutter with a control for opening the
seat in opposition to a resilient recall member. A pilot duct leads
from the main duct to supply a pilot burner, the main duct includes
a magnetic thermoelectric safety unit which is manually or
automatically armed, acting on the pilot duct to enable gas to flow
to the pilot burner when armed. The pilot duct includes a pressure
regulator having a shutter with a membrane control, the membrane
subject to pressure regulated by the regulator and to a calibration
pressure determined in a calibration chamber of the regulator. The
device includes a fluid connector between the calibration chamber
and the main valve to provide a pressure signal correlated with the
gas supply pressure.
Inventors: |
TURRIN; Gianpiero; (Padova,
IT) |
Assignee: |
SIT LA PRECISA S.P.A. CON SOCIO
UNICO
Padova
IT
|
Family ID: |
43737202 |
Appl. No.: |
13/326100 |
Filed: |
December 14, 2011 |
Current U.S.
Class: |
122/14.21 ;
431/42 |
Current CPC
Class: |
F23N 2235/18 20200101;
F23N 1/007 20130101; F23N 1/005 20130101; F23N 2235/24 20200101;
F23N 2235/14 20200101; F23N 2235/20 20200101 |
Class at
Publication: |
122/14.21 ;
431/42 |
International
Class: |
F24H 9/20 20060101
F24H009/20; F23Q 9/00 20060101 F23Q009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 27, 2010 |
IT |
PD2010A000393 |
Claims
1. A device for controlling the supply of fuel gas to a burner
comprising: a main duct for supplying the gas between an inlet
section and an outlet section, the main duct being provided with at
least one main valve including a respective valve seat associated
with a corresponding shutter with a respective control for opening
of the seat in opposition to a respective resilient recall member,
a pilot duct for supplying a pilot burner leading from the main
duct upstream of at least the one main valve, the main duct being
provided, upstream of at least the one main valve, with a magnetic
thermoelectric safety unit with a manually armed switch or with an
automatic arming system, which acts on the pilot duct to enable the
gas to flow to the pilot burner when the unit is armed, the pilot
duct being provided with a pressure regulator having a shutter with
a membrane control, the membrane being subject on one hand to the
pressure regulated by the regulator and on the other hand to a
calibration pressure determined in a calibration chamber of the
regulator, a calibration spring being provided in the chamber and
acting on the membrane, and a fluid connector between the
calibration chamber of the pressure regulator and at least the one
main valve, in order to supply to the calibration chamber a
pressure signal correlated with the gas supply pressure when
supplied to the main duct such that the pressure regulated by the
regulator can be regulated at least to a first level, when there is
no gas supply in the main duct, and to a second level, greater than
the first level, when gas is being supplied in the main duct, the
flow of gas supplied to the pilot duct being correlated with the
respective levels of the pressure signal supplied to the
calibration chamber.
2. The device according to claim 1, wherein the fluid connector
comprises a connection duct extending between the calibration
chamber and a section of the main supply duct downstream of the
valve seat of at least the one main valve with respect to the
direction of flow of the gas, the pressure signal supplied to the
calibration chamber corresponding to the gas supply pressure
obtained through the main valve.
3. The device according to claim 1, wherein at least the one main
valve comprises a respective control electrovalve with a mechanical
or electric operator to control opening/closing of the main valve,
the electrovalve configured to open/close a drive duct of a
respective servo-assisted drive circuit so as indirectly to
control, by the membrane control, the respective shutter of the
corresponding valve, the respective duct of the drive circuit
bringing the main duct into fluid communication with a respective
drive chamber of the main valve, one side of the membrane of the
membrane control being subject to pressure in the respective drive
chamber, the fluid connector comprising a duct connecting the
calibration chamber of the pressure regulator and a section of the
drive duct of the valve, the section being disposed between the
electrovalve and the drive chamber.
4. The according to claim 2, wherein the pressure signal supplied
to the calibration chamber of the regulator, by the connection
duct, is correlated with a regulated gas supply pressure supplied
to the burner when the main valve is in an open position.
5. The device according to claim 3, wherein the pressure signal
supplied to the calibration chamber of the regulator, by the
connection duct, is correlated with a regulated gas supply pressure
supplied to the burner when the main valve is in an open position.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a device for controlling
the supply of fuel gas to a burner. The invention is applied in
particular, although not exclusively, in the sector of devices for
the multi-function control of the supply of fuel gases to valve
units designed for uses in heating appliances, in particular
domestic water heater appliances.
BACKGROUND
[0002] In a typical known solution with respect to these devices, a
magnetic safety unit with a pilot and a thermocouple is associated
with a relative manual arming system and with at least one valve
having a mechanical or electrical operator for controlling a gas
supply to a main burner directly or indirectly (servo-assisted
system).
[0003] In these applications, it is also known to provide a pilot
duct through which a predetermined flow of gas, correlated with the
pressure regulated by a pressure regulator disposed in the pilot
duct, is supplied in order to supply the pilot burner flame.
[0004] As a result, the flow supplied to the pilot burner is the
same during both operation of the pilot burner alone, when the main
gas throughput is intercepted, and during operation of the main
burner.
[0005] It would be preferable, however, to reduce the rate of flow
in the rest phases of the pilot burner, when only the pilot flame
is ignited, with a view to efficient saving of fuel gas (with the
pilot introducing less energy into the system), while at the same
time ensuring a higher flow of gas to the pilot to facilitate
ignition of the main burner.
[0006] The object of the present invention is to provide a device
for controlling the supply of fuel gas to a main burner, in
particular for water heater appliances, which is structurally and
functionally designed to ensure levels of flow to the pilot burner
which are appropriate for the various operating stages, with more
efficient fuel consumption when only the pilot burner is
ignited.
[0007] This object is achieved by a device for controlling the
supply of fuel gas to a burner embodied in accordance with the
appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Other advantages and features of the present invention will
become clear from the following detailed description of preferred
embodiments thereof, given with reference to the appended drawings
which are provided purely by way of non-limiting example and in
which:
[0009] FIG. 1 is a diagrammatic view in longitudinal section of a
first embodiment of the control device of the invention;
[0010] FIG. 2 is a similar view to FIG. 1 of a second embodiment of
the control device of the invention;
[0011] FIG. 3 is a similar view to the preceding Figures of a third
embodiment of the control device of the invention;
[0012] FIG. 4 is a similar view to the preceding Figures of a
fourth embodiment of the control device of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0013] With reference, first, to FIG. 1, a device for controlling
the supply of fuel gas to a burner of a domestic water heater
embodied in accordance with the present invention, is shown overall
by 1.
[0014] The device 1 comprises a valve unit disposed in a main gas
supply duct 2 between a gas inlet section 3 and an outlet section 4
where the gas is supplied to a main burner 4a.
[0015] A main valve, shown overall by 5, is disposed along the main
duct 2. The valve 5 comprises a valve seat 5a associated with a
respective shutter 5b, for instance with membrane control 5c for
the opening of the seat 5a in opposition to a respective resilient
recall member such as a respective spring 5d.
[0016] The valve 5 acts as an on/off valve for the safe closure of
the main gas channel, as will be described in detail below.
[0017] The valve 5 may be associated with an electrovalve for
controlling the servo-assisted circuit, shown by 7, disposed to
open and close an auxiliary duct 8 for driving the servo-circuit,
which forms the take-up duct for the pressure signal to be
transferred to the drive chamber of the servo-circuit. The membrane
5c acts directly on a control stem 5e of the shutter 5b which is in
turn urged to close the seat by the spring 5d.
[0018] One side of the membrane 5c defines a drive chamber 10 which
communicates with the main duct 2, upstream of the valve 5, via the
duct 8.
[0019] More particularly, the duct 8 has a first portion 8a,
extending upstream of the electrovalve 7, and a second portion 8b,
prolonging the first, extending downstream of the electrovalve 7
and communicating with the chamber 10. A throttle 30 is provided in
the duct portion 8b.
[0020] The drive chamber 10 is connected to the main duct 2,
downstream of the valve seat 5a of the valve 5, by a respective
discharge duct 28 in which a pressure regulator, shown overall by
32, is provided. The regulator is a membrane pressure regulator,
known per se, in which one side of the membrane defines a drive
chamber 33 communicating, by means of a portion 28a of the duct 28,
with the main duct 2 (downstream of the valve 5) and is also able
to intercept the output section of the other portion 28b of the
duct 28 communicating with the drive chamber 10. The opposite side
of the membrane is urged by a calibration spring 35 disposed in a
chamber open to atmosphere via an opening 36. The pressure
regulator 32 is designed to react to the supply pressure variations
and to compensate them and return the pressure to a calibration
value predetermined by regulation of the spring 35.
[0021] The pressure regulator 32 may also be designed with a
pressure modulation function, for instance as a modulating
regulator of electromagnetic type (by means of a motor, linear
actuator) or of pneumatic (membrane) type.
[0022] At the location of the electrovalve 7, the relative portion
of the duct 8 may be opened and closed at will by an electromagnet
11, of on/off type with resilient recall, acting on a shutter
member 12 associated with the throughput section of the duct 8
which may be displaced to and from a position intercepting the
throughput section.
[0023] The valve unit of the device of the invention comprises an
auxiliary gas line, branching from the main line, via which a pilot
burner 16 is supplied. The auxiliary line has a pilot duct 16a
which branches from the main duct 2 in order to supply the pilot
burner 16.
[0024] Starting from the inlet section, in the main duct 2, there
is a first section 18' prolonged by a second section 18'' via an
interposed valve seat 18, on which a magnetic thermoelectric safety
unit with manual arming 20 (or, as an alternative, with an
automatic arming system) acts, this unit including a shutter 18a
which is held in the position opening the seat 18 by the excitation
of the magnetic unit generated by the voltage of a thermocouple
(not shown) when there is a flame at the pilot burner 16.
[0025] The section 18'' communicates with the main duct 2,
downstream of the seat 18, and with the drive duct 8.
[0026] The section 18'', extending downstream of the seat 18, is
also connected with the pilot duct 16a via an interposed valve seat
20a.
[0027] A shutter 20b rigid with the control stem 20c of a knob
member 20d of the magnetic unit acts on the valve seat 20a.
[0028] The drawing shows a top view of the knob 20d illustrating
the operating positions which may be selected (OFF, PILOT, ON).
[0029] The knob member 20d is connected to the actuator stem 20c to
carry out the manual arming of the safety unit, in a manner known
per se, in which, in the arming position (PILOT), the ignition of
an ignition member (not shown, for instance of piezoelectric type)
associated with the pilot burner 16, is simultaneously controlled.
The knob 20d may also be switched to the closed position (OFF) in
which the valve seats 18 and 20a are intercepted by the
corresponding shutters of the magnetic safety unit.
[0030] A pressure regulator 40, with membrane control, designed to
regulate the pressure of the gas and therefore the flow supplied to
the pilot burner 16 operates in the pilot duct 16a.
[0031] The pressure regulator 40 includes a servovalve forming a
valve seat 40a cooperating with a shutter shown diagrammatically at
40b, whose control stem 40c is rigidly connected to a control
membrane 41 for its control. The membrane 41 is subject on one hand
to the pressure regulated by the regulator device and on the other
hand to a pressure established in a calibration chamber 42 of the
regulator and to the resilient force of a spring 43.
[0032] According to the invention, a connection duct 45 is provided
and brings the calibration chamber 42 into fluid communication with
a section of the main duct 2 downstream of the valve 5, i.e. in a
valve portion subject to a gas pressure when the shutters 12 and 5
are in the open position.
[0033] As an alternative, it is possible for the connection duct 45
to bring the chamber 42 into fluid communication with a section of
the portion 8b of the duct 8 disposed downstream of the
electrovalve 7.
[0034] The pressure signal downstream of the valve 5 (or in the
above-mentioned alternative version, in the section 8b of the drive
duct), is supplied to the calibration chamber 42 via the duct
45.
[0035] It is possible, as a result of the provision of the
connection duct 45, to obtain two separate pressure (and therefore
flow) levels in the gas supplied via the pilot duct.
[0036] A first pressure level is generated in the pilot duct when
the valve 5 is in the closed condition (with the valve 7
closed).
[0037] At this stage, as no gas is passing through the electrovalve
7, no pressure correlated with the supply pressure is determined in
the main duct downstream of the valve 5 (or, in the above-mentioned
alternative version, in the portion 8b of the duct 8) and the
regulator therefore determines a pressure correlated solely with
the resilient force of the spring 43 which causes a first level of
supply flow to the pilot burner to maintain the pilot flame (the
main burner is not activated).
[0038] The subsequent opening of the valve seat 5, by excitation of
the electrovalve 7, causes, in the main duct downstream of the
valve 5 (or, in the above-mentioned alternative version, in the
portion 8b of the duct 8), a pressure signal equal to or correlated
with the supply pressure in the main duct, which signal,
transferred by means of the duct 45 to the calibration chamber 42,
determines a second pressure level regulated by the regulator,
greater than the first level, and such as to enable the ignition of
the main burner to which the gas flow is supplied after opening of
the main duct 2.
[0039] It is thus possible to obtain a so-called `two-stage` pilot
burner 16, with a first reduced flow level designed solely to
maintain the pilot burner flame, and a second higher flow level
designed to ignite the main burner.
[0040] FIG. 2 shows a second embodiment of the device of the
invention, in which details similar to those of the previous
embodiment bear the same reference numerals.
[0041] In this embodiment, the control device is applied to a valve
of thermostat type, of the so-called `thermo-mechanical thermostat`
type, in which the valve seat 5a obtained in the main duct 2 is
associated with a corresponding shutter 5b controlled by a
thermo-mechanical actuator 50. A valve unit of this type is
disclosed in Italian Patent Application PD2000A000138, in the name
of the Applicants, whose specification is understood to be fully
included here for any detail which is not described in detail
below.
[0042] The above-mentioned actuator comprises a member 51 sensitive
to water temperature variations which is disposed in contact with
the water to be heated and is connected in operation to the shutter
5b of the valve. As a result of the thermal expansion of this
member, a displacement correlated with the variation of the water
temperature is generated, by a bi-stable elastic device 52, with
respect to the control stem 5c of the shutter, as a result of which
the shutter is caused to close the corresponding valve seat to
intercept the flow of gas when a predetermined temperature value is
exceeded.
[0043] In this embodiment, the device of the invention connects the
calibration chamber 42, by means of the duct 45, with a section of
the main duct 2 disposed downstream of the valve seat 5 with
respect to the direction of the flow of gas, thus obtaining the
two-stage pilot function described above.
[0044] FIG. 3 shows a third embodiment of the device of the
invention, in which details similar to those of the previous
embodiments bear the same reference numerals.
[0045] In this embodiment, the control device is applied to a valve
unit in which a pair of main servo-valves 5, 6 are provided in
cascade with one another and a draught switch 55 of pneumatic type
is disposed in the combustion fume discharge duct 56. A valve unit
of this type is disclosed in Italian Patent Application
PD2010A000385, in the name of the Applicants, whose specification
is understood to be fully included here for any detail which is not
described in detail below.
[0046] Similarly to the previous embodiment, the device of the
invention connects the calibration chamber 42, by means of the duct
45, with the section of the main duct 2 disposed downstream of the
valve seat 6a of the servo-valve 6 with respect to the direction of
the flow of gas, thus obtaining the two-stage pilot function
described above.
[0047] FIG. 4 shows a fourth embodiment of the device of the
invention, in which details similar to those of the previous
embodiments bear the same reference numerals.
[0048] This embodiment differs from the preceding embodiment
chiefly in that it includes a draught switch 55 with a motor-driven
actuator 60, as shown diagrammatically in the corresponding Figure.
Similarly to the previous embodiment, the calibration chamber 42 of
the regulator is connected, via the duct 45, with the section of
the main duct 2 disposed downstream of the valve seat 6a of the
servo-valve 6 with respect to the direction of the flow of gas,
thus obtaining the two-stage pilot function described above.
[0049] The invention thus achieves the above-mentioned objects and
also achieves the advantages listed with respect to known
solutions. It should in particular be noted that it is possible, as
a result of the invention, substantially to reduce the energy
introduced into the system by the pilot burner during the "rest"
stage in which no gas passes through the main duct in the direction
of the main burner.
[0050] A device for controlling the supply of fuel gas to a burner,
in particular for water heater appliances
SPECIFICATION
[0051] The present invention relates to a device for controlling
the supply of fuel gas to a burner in accordance with the features
set out in the preamble of claim 1. The invention is applied in
particular, although not exclusively, in the sector of devices for
the multi-function control of the supply of fuel gases to valve
units designed for uses in heating appliances, in particular
domestic water heater appliances.
[0052] In a typical known solution with respect to these devices, a
magnetic safety unit with a pilot and a thermocouple is associated
with a relative manual arming system and with at least one valve
having a mechanical or electrical operator for controlling a gas
supply to a main burner directly or indirectly (servo-assisted
system).
[0053] In these applications, it is also known to provide a pilot
duct through which a predetermined flow of gas, correlated with the
pressure regulated by a pressure regulator disposed in the pilot
duct, is supplied in order to supply the pilot burner flame.
[0054] As a result, the flow supplied to the pilot burner is the
same during both operation of the pilot burner alone, when the main
gas throughput is intercepted, and during operation of the main
burner.
[0055] It would be preferable, however, to reduce the rate of flow
in the rest phases of the pilot burner, when only the pilot flame
is ignited, with a view to efficient saving of fuel gas (with the
pilot introducing less energy into the system), while at the same
time ensuring a higher flow of gas to the pilot to facilitate
ignition of the main burner.
[0056] The object of the present invention is to provide a device
for controlling the supply of fuel gas to a main burner, in
particular for water heater appliances, which is structurally and
functionally designed to ensure levels of flow to the pilot burner
which are appropriate for the various operating stages, with more
efficient fuel consumption when only the pilot burner is
ignited.
[0057] This object is achieved by a device for controlling the
supply of fuel gas to a burner embodied in accordance with the
appended claims.
[0058] Other advantages and features of the present invention will
become clear from the following detailed description of preferred
embodiments thereof, given with reference to the appended drawings
which are provided purely by way of non-limiting example and in
which:
[0059] FIG. 1 is a diagrammatic view in longitudinal section of a
first embodiment of the control device of the invention;
[0060] FIG. 2 is a similar view to FIG. 1 of a second embodiment of
the control device of the invention;
[0061] FIG. 3 is a similar view to the preceding Figures of a third
embodiment of the control device of the invention;
[0062] FIG. 4 is a similar view to the preceding Figures of a
fourth embodiment of the control device of the invention.
[0063] With reference, first, to FIG. 1, a device for controlling
the supply of fuel gas to a burner of a domestic water heater
embodied in accordance with the present invention, is shown overall
by 1.
[0064] The device 1 comprises a valve unit disposed in a main gas
supply duct 2 between a gas inlet section 3 and an outlet section 4
where the gas is supplied to a main burner 4a.
[0065] A main valve, shown overall by 5, is disposed along the main
duct 2. The valve 5 comprises a valve seat 5a associated with a
respective shutter 5b, for instance with membrane control 5c for
the opening of the seat 5a in opposition to a respective resilient
recall means such as a respective spring 5d.
[0066] The valve 5 acts as an on/off valve for the safe closure of
the main gas channel, as will be described in detail below.
[0067] The valve 5 may be associated with an electrovalve for
controlling the servo-assisted circuit, shown by 7, disposed to
open and close an auxiliary duct 8 for driving the servo-circuit,
which forms the take-up duct for the pressure signal to be
transferred to the drive chamber of the servo-circuit. The membrane
5c acts directly on a control stem 5e of the shutter 5b which is in
turn urged to close the seat by the spring 5d.
[0068] One side of the membrane 5c defines a drive chamber 10 which
communicates is with the main duct 2, upstream of the valve 5, via
the duct 8.
[0069] More particularly, the duct 8 has a first portion 8a,
extending upstream of the electrovalve 7, and a second portion 8b,
prolonging the first, extending downstream of the electrovalve 7
and communicating with the chamber 10. A throttle 30 is provided in
the duct portion 8b.
[0070] The drive chamber 10 is connected to the main duct 2,
downstream of the valve seat 5a of the valve 5, by a respective
discharge duct 28 in which a pressure regulator, shown overall by
32, is provided. The regulator is a membrane pressure regulator,
known per se, in which one side of the membrane defines a drive
chamber 33 communicating, by means of a portion 28a of the duct 28,
with the main duct 2 (downstream of the valve 5) and is also able
to intercept the output section of the other portion 28b of the
duct 28 communicating with the drive chamber 10. The opposite side
of the membrane is urged by a calibration spring 35 disposed in a
chamber open to atmosphere via an opening 36. The pressure
regulator 32 is designed to react to the supply pressure variations
and to compensate them and return the pressure to a calibration
value predetermined by regulation of the spring 35.
[0071] The pressure regulator 32 may also be designed with a
pressure modulation function, for instance as a modulating
regulator of electromagnetic type (by means of a motor, linear
actuator) or of pneumatic (membrane) type.
[0072] At the location of the electrovalve 7, the relative portion
of the duct 8 may be opened and closed at will by an electromagnet
11, of on/off type with resilient recall, acting on a shutter
member 12 associated with the throughput section of the duct 8
which may be displaced to and from a position intercepting the
throughput section.
[0073] The valve unit of the device of the invention comprises an
auxiliary gas line, branching from the main line, via which a pilot
burner 16 is supplied. The auxiliary line has a pilot duct 16a
which branches from the main duct 2 in order to supply the pilot
burner 16.
[0074] Starting from the inlet section, in the main duct 2, there
is a first section 18' prolonged by a second section 18'' via an
interposed valve seat 18, on which a magnetic thermoelectric safety
unit with manual arming 20 (or, as an alternative, with an
automatic arming system) acts, this unit including a shutter 18a
which is held in the position opening the seat 18 by the excitation
of the magnetic unit generated by the voltage of a thermocouple
(not shown) when there is a flame at the pilot burner 16.
[0075] The section 18'' communicates with the main duct 2,
downstream of the seat 18, and with the drive duct 8.
[0076] The section 18'', extending downstream of the seat 18, is
also connected with the pilot duct 16a via an interposed valve seat
20a.
[0077] A shutter 20b rigid with the control stem 20c of a knob
member 20d of the magnetic unit acts on the valve seat 20a.
[0078] The drawing shows a top view of the knob 20d illustrating
the operating positions which may be selected (OFF, PILOT, ON).
[0079] The knob member 20d is connected to the actuator stem 20c to
carry out the manual arming of the safety unit, in a manner known
per se, in which, in the arming position (PILOT), the ignition of
an ignition member (not shown, for instance of piezoelectric type)
associated with the pilot burner 16, is simultaneously controlled.
The knob 20d may also be switched to the closed position (OFF) in
which the valve seats 18 and 20a are intercepted by the
corresponding shutters of the magnetic safety unit.
[0080] A pressure regulator 40, with membrane control, designed to
regulate the pressure of the gas and therefore the flow supplied to
the pilot burner 16 operates in the pilot duct 16a.
[0081] The pressure regulator 40 includes a servovalve forming a
valve seat 40a cooperating with a shutter shown diagrammatically at
40b, whose control stem 40c is rigidly connected to a control
membrane 41 for its control. The membrane 41 is subject on one hand
to the pressure regulated by the regulator device and on the other
hand to a pressure established in a calibration chamber 42 of the
regulator and to the resilient force of a spring 43. According to
the invention, a connection duct 45 is provided and brings the
calibration chamber 42 into fluid communication with a section of
the main duct 2 downstream of the valve 5, i.e. in a valve portion
subject to a gas pressure when the shutters 12 and 5 are in the
open position.
[0082] As an alternative, it is possible for the connection duct 45
to bring the chamber 42 into fluid communication with a section of
the portion 8b of the duct 8 disposed downstream of the
electrovalve 7.
[0083] The pressure signal downstream of the valve 5 (or in the
above-mentioned alternative version, in the section 8b of the drive
duct), is supplied to the calibration chamber 42 via the duct
45.
[0084] It is possible, as a result of the provision of the
connection duct 45, to obtain two separate pressure (and therefore
flow) levels in the gas supplied via the pilot duct.
[0085] A first pressure level is generated in the pilot duct when
the valve 5 is in the closed condition (with the valve 7
closed).
[0086] At this stage, as no gas is passing through the electrovalve
7, no pressure correlated with the supply pressure is determined in
the main duct downstream of the valve 5 (or, in the above-mentioned
alternative version, in the portion 8b of the duct 8) and the
regulator therefore determines a pressure correlated solely with
the resilient force of the spring 43 which causes a first level of
supply flow to the pilot burner to maintain the pilot flame (the
main burner is not activated).
[0087] The subsequent opening of the valve seat 5, by excitation of
the electrovalve 7, causes, in the main duct downstream of the
valve 5 (or, in the above-mentioned alternative version, in the
portion 8b of the duct 8), a pressure signal equal to or correlated
with the supply pressure in the main duct, which signal,
transferred by means of the duct 45 to the calibration chamber 42,
determines a second pressure level regulated by the regulator,
greater than the first level, and such as to enable the ignition of
the main burner to which the gas flow is supplied after opening of
the main duct 2.
[0088] It is thus possible to obtain a so-called `two-stage` pilot
burner 16, with a first reduced flow level designed solely to
maintain the pilot burner flame, and a second higher flow level
designed to ignite the main burner.
[0089] FIG. 2 shows a second embodiment of the device of the
invention, in which details similar to those of the previous
embodiment bear the same reference numerals.
[0090] In this embodiment, the control device is applied to a valve
of thermostat type, of the so-called `thermo-mechanical thermostat`
type, in which the valve seat 5a obtained in the main duct 2 is
associated with a corresponding shutter 5b controlled by a
thermo-mechanical actuator 50. A valve unit of this type is
disclosed in Italian Patent Application PD2000A000138, in the name
of the Applicants, whose specification is understood to be fully
included here for any detail which is not described in detail
below.
[0091] The above-mentioned actuator comprises a member 51 sensitive
to water temperature variations which is disposed in contact with
the water to be heated and is connected in operation to the shutter
5b of the valve. As a result of the thermal expansion of this
member, a displacement correlated with the variation of the water
temperature is generated, by a bi-stable elastic device 52, with
respect to the control stem 5c of the shutter, as a result of which
the shutter is caused to close the corresponding valve seat to
intercept the flow of gas when a predetermined temperature value is
exceeded.
[0092] In this embodiment, the device of the invention connects the
calibration chamber 42, by means of the duct 45, with a section of
the main duct 2 disposed downstream of the valve seat 5 with
respect to the direction of the flow of gas, thus obtaining the
two-stage pilot function described above. FIG. 3 shows a third
embodiment of the device of the invention, in which details similar
to those of the previous embodiments bear the same reference
numerals.
[0093] In this embodiment, the control device is applied to a valve
unit in which a pair of main servo-valves 5, 6 are provided in
cascade with one another and a draught switch 55 of pneumatic type
is disposed in the combustion fume discharge duct 56. A valve unit
of this type is disclosed in Italian Patent Application
PD2010A000385, in the name of the Applicants, whose specification
is understood to be fully included here for any detail which is not
described in detail below.
[0094] Similarly to the previous embodiment, the device of the
invention connects the calibration chamber 42, by means of the duct
45, with the section of the main duct 2 disposed downstream of the
valve seat 6a of the servo-valve 6 with respect to the direction of
the flow of gas, thus obtaining the two-stage pilot function
described above.
[0095] FIG. 4 shows a fourth embodiment of the device of the
invention, in which details similar to those of the previous
embodiments bear the same reference numerals.
[0096] This embodiment differs from the preceding embodiment
chiefly in that it includes a draught switch 55 with a motor-driven
actuator 60, as shown diagrammatically in the corresponding Figure.
Similarly to the previous embodiment, the calibration chamber 42 of
the regulator is connected, via the duct 45, with the section of
the main duct 2 disposed downstream of the valve seat 6a of the
servo-valve 6 with respect to the direction of the flow of gas,
thus obtaining the two-stage pilot function described above.
[0097] The invention thus achieves the above-mentioned objects and
also achieves the advantages listed with respect to known
solutions. It should in particular be noted that it is possible, as
a result of the invention, substantially to reduce the energy
introduced into the system by the pilot burner during the "rest"
stage in which no gas passes through the main duct in the direction
of the main burner.
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