CN107949748A - Electric guide's static valve for gas burner - Google Patents

Abstract

The object of the invention is an electric actuator (1) for gas hobs and the like, piloted by an actuating device comprising: at least one safety electromagnet (4) forming part of a pilot stabilizer; at least one fuel gas a shut-off device (2), which is substantially a bushing with an outlet channel (22) and a conduit (23) for fuel gas, at least one safety shutter (20) on which a compressive/tensile _force (FF ) acts so that Said exit channel (22) is securely closed; at least one service shutter (20); a support structure (10) having a cavity (100) in which a rod (21) is slidably placed, in contact with said safety electromagnet ( 4) Cooperating at least one ferromagnetic element (32) and said shutter (20) cooperating with fuel gas shut-off means (2) are constrained by it, wherein said safety shutter (20) and said service shutter (20) Coincident on the same shutter (20); said ferromagnetic elements (32) are anchored by the mutual attracting anchoring force (F _P ) that occurs when said safety electromagnet (4) is energized especially by the flame sensor of the pilot stabilizer to said safety electromagnet (4), characterized in that said compressive/pull _force (FF) is of magnetic nature, which is easily controlled by the command force ( _FS ) applied for opening of said outlet channel (22) and said The above anchoring force (F _P ) exceeds.

Description

Electro-pilot static valves for gas burners

technical field

The present invention relates to an electro-pilot static system for gas burners, in particular an electric actuator for gas hobs and the like equipped with a safety system.

Background technique

The current state of the art offers different solutions for the distribution and regulation of fuel gas for stoves, also considering different systems for ensuring safety.

For example, ordinary stoves are equipped with a safety system, advantageously comprising valves, which automatically stop the flow of fuel gas to the burners in the event of accidental shut-off of the flame.

A well known and used solution provides for the use of linear shut-off valves mounted sequentially relative to manually regulating valves, usually rotary plug valves (mouths).

By interacting with the plug, the user performs a manual operation that moves the shutter of the safety valve backwards so that the ferromagnetic holder restrained by it comes into contact with the electromagnet, allowing the passage of gas for the ignition of the burner; The electromagnet is controlled and supplied by the flame detector.

The flame detector usually utilizes a thermocouple placed near the burner flame; in the presence of the flame, the thermocouple creates a potential difference that produces a current that supplies the solenoid of the electromagnet.

The magnetic field created by the solenoid is sufficient to hold the shutter in its open position and ensure fuel gas is supplied to the burner.

In case of accidental extinguishment of the flame, the thermocouple no longer produces any potential difference, whereby it stops supplying power to the solenoid of the electromagnet, which is no longer able to generate a magnetic field sufficient to hold the shutter, in a resilient device (such as a spring) The shutter returns to the rest position under the thrust of the valve, closing the valve thereby interrupting the gas flow; this avoids that in the event of inadvertently shutting down the flame, the gas continues to be conveyed by the valve and dispersed in the surrounding indoor environment (usually a kitchen or rooms where food and meals are prepared and cooked), posing a serious risk to people and things.

Solenoid-thermocouple couplings are known to be "pilot static" and are used extensively with each burner to ensure safe use of the range.

The various solutions proposed according to the prior art propose to keep the equipment suitable for controlling and regulating the gas flow separate and distinct from the equipment suitable for safety.

Said segmentation concerns the installation of several components in cookers and the like, where the nature of the overall size is extremely relevant and saving space is one of the goals pursued by designers and manufacturers.

Normally closed globe valves on the market realize the passage of gas through remote electrical control.

In fact, for safety reasons, the shut-off valves are closed in the rest position, while in the working position they are continuously kept open by a continuous control signal.

This configuration of operation involves energy waste and heating of electrical and electronic equipment; the latter may over time produce degradation of cable insulation and deterioration of the same circuits, leading to failure or damage.

Contents of the invention

The main object of the present invention is to provide an electric actuator for gas hobs and the like which combines in a single element the parts related to safety and the parts related to flow regulation.

In particular, the main object of the present invention is to provide an electric actuator for gas hobs and the like, which integrates in a single element the flow regulation of the fuel gas and the automatic cut-off of the fuel gas in case of an accidental shut-off of the flame .

Another object of the present invention is to provide an electric actuator for gas hobs and the like, which allows the control and regulation of the device to supply the air flow only during its actuation, suspending the supply of electric energy once the regulation is completed.

The above objects and others which will appear clearly hereinafter are achieved by an electric drive for gas hobs and the like described in the following description and the appended claims forming an integral part of this description.

Brief description of the drawings

Further features of the invention are better emphasized by the following description of preferred embodiments according to the patent claims and are shown in the table of drawings by way of non-limiting example only, in which:

- Figure 1 shows a sectional view of an electric actuator in a closed or rest position according to a first embodiment of the invention;

- Figure 2 shows a sectional view of the electric actuator in the open or working position according to the first embodiment of the invention;

- Figure 3 shows a cross-sectional view of the electric actuator in the closed or rest position according to a second embodiment of the invention;

- Figure 4 shows a cross-sectional view of the electric actuator in the open or working position according to the second embodiment of the invention;

- Figure 5 shows a sectional view of an electric actuator according to another implementation variant of the invention;

- Figure 6 shows an electric actuator with a membrane according to the invention;

- Figure 7 compares two cross-sectional views of an electric actuator according to the invention in an open condition and in a closed condition.

- Figure 8 shows a summary table of parameters and operating configurations of the electric actuator according to the invention;

- Figures 9a and 9b show two examples of gas valves suitable for blast air burners, in which an electric actuator according to the invention can be used.

Unless otherwise stated, any possible spatial references in this report, such as the terms up/down, front/back, right/left, etc., refer to the position of elements shown in the drawings.

Features of the invention are described using reference numerals in the figures.

With reference to the accompanying drawings, an electric actuator 1 according to the invention for gas hobs and the like has a safety electromagnet 4, a shut-off device 2 for fuel gas, a sleeve equipped with an outlet channel 22 and a fuel gas duct 23, and said shut-off device 2 cooperating at least one service shutter 20 and at least one safety shutter 20 on which a compressive/pull force acts to securely close said electric actuator 1 , advantageously said pressure/pull force being of magnetic or elastic nature.

The service shutter and the safety shutter coincide on the same shutter 20, which simultaneously performs two tasks:

- cutting off the fuel gas to be sent to the burner;

- Shut-off device 2 for safe closing of fuel gas when the burner or flame is switched off.

Said compressive/pull force acts on said shutter 20, operating the safety closing of the electric actuator 1, in particular said pressure operates the safety closing of said outlet channel 22 of the fuel gas.

The electric actuator 1 comprises a support structure 10, substantially tubular and preferably made of non-magnetic material, at each end of which is mounted a safety electromagnet arrangement 4 and a fuel gas cut-off arrangement 2 (essentially a sleeve) .

In said support structure 10 a cavity 100 is provided, in which a rod 21 is slidably placed, which has an element 30 sensitive to a magnetic field. A suitably controlled lever 21 acts to open and/or close the shut-off device 2 for fuel gas.

A detailed description of the drawings is provided below by way of non-limiting examples.

Figure 1 shows a cross-sectional view of an electric actuator according to the invention in a closed or rest position.

In said support structure 10 there is provided a cavity 100 provided with a base 101 in which is placed a slider 30 integrated with a rod 21 , said slider 30 being sensitive to a magnetic field.

Said base 101 cooperates with the slider 30 to achieve the magnetic force that operates the safety closure of the electric actuator 1 according to the invention.

In this construction variant, the slider 30 comprises a permanent magnet, while the base 101 comprises a ferromagnet.

According to an alternative embodiment, said slider 30 may advantageously comprise a ferromagnetic body, while the base 101 may comprise a permanent magnet, without altering the correct operation of the electric actuator 1, or both the slider 30 and the base 101 may comprise a permanent magnet .

In general, due to the material from which they are made and their mutual position, the magnetic interaction between the base 101 and the vernier 30 must be ensured for any condition of use and for any position of the shutter 20 or electromagnet 4 ("normally closed") "condition).

In order to ensure the "normally closed" condition of the electric actuator 1, the position of the wiper 30 and the bottom 101, the material from which they are made and the opening and/or closing mode of the burner are parameters to be selected and to be defined.

Said base 101 , comprising a disk of ferromagnetic material, has a central hole 111 for the passage and sliding of a rod 21 integral with said slider 30 .

One end of said rod 21 , advantageously made of non-magnetic material, has at least one ferromagnetic element 32 cooperating with the safety electromagnetic device 4 ; the other end of the rod 21 is integral with the shutter 20 .

The shutter 20 cooperates with the bushing 2 of the fuel gas; in particular, the shutter 20 opens or closes the outlet channel 22 of the fuel gas, allowing the fuel gas to pass from the duct 23 to said outlet channel 22, towards the corresponding burner (not shown) .

With reference to the prior art, the safety electromagnet 4 is advantageously controlled by means of thermocouples placed near the burner flame zone, as shown and described above.

Thus, when the burner is off, the thermocouple does not supply any type of current to said electromagnet 4, which is then de-energized and does not generate any magnetic field; in this case, between the electromagnet 4 and the ferromagnetic element 32 There are no significant interactions of any kind.

In FIG. 1 , the electric actuator 1 is in the closed position and the shutter 20 closes the outlet channel 22 for fuel gas.

Closing of the electric actuator 1 according to the variant of the invention is ensured by the magnetic force between the vernier 30 and the bottom 101; said magnetic force fixes and stabilizes the rod 21 in order to lock the shutter 20 at the mouth of the outlet channel 22 of the fuel gas , to prevent the entry of fuel gas.

By analyzing the closed configuration represented in FIG. 1 in more detail, it can be deduced that the only active force is the magnetic force between the bottom 101 and the wiper 30 .

In fact, the electromagnet 4 is de-energized, so there is no apparent attractive magnetic force between said electromagnet 4 and the ferromagnetic element 32; thus, by the attractive magnetic force between the bottom 101 and the vernier 30, the rod 21 is directed towards Casing 2 translates.

Said magnetic force achieves and guarantees the shut-off of the electric actuator 1 , engaging the shutter 22 at the mouth of the outlet channel 22 of the fuel gas, thereby closing it.

Figure 2 shows a cross-sectional view of an electric actuator according to the invention in an open or working position.

In the figure, the electric actuator 1 is visible in the open position, ie the outlet channel 22 for fuel gas communicates with the duct 23 for fuel gas.

Considering Figures 1 and 2, let us assume that it is desired to turn on the burners of the stove.

Via suitable actuating means (not shown), the user manually activates the electric actuator 1 by translating the rod 21 towards said electromagnet 4 , bringing the ferromagnetic element 32 into contact with said electromagnet 4 .

The shutter 20, positioned on the rod 21, is moved away from the outlet channel 22 of said fuel gas, thus allowing the gas to enter from the outlet channel 22 and reach the burner, allowing it to be opened.

When the flame of the burner is switched on, the thermocouple starts to generate a current which excites the electromagnet 4 , ensuring the magnetic coupling between said electromagnet 4 and the ferromagnetic element 32 .

In fact, the attractive magnetic force between the electromagnet 4 and the ferromagnetic element 32 is greater than the attractive magnetic force existing between the wiper 30 and the base 101 ; this allows to keep the electromagnet 4 and the ferromagnetic element 32 integral.

With the flame turned on, the mechanical action (applied by the user via the actuating device) to keep the electromagnet 4 and ferromagnetic element 32 in contact is suspended and the valve opening is ensured by a thermocouple that generates the energy required to keep the electromagnet 4 energized. current.

The passage of gas is ensured by said mechanical action keeping the ferromagnetic element 32 in contact with the electromagnet 4 during the transition period from the user giving the opening command to the thermocouple being put into operation.

In case of an accidental shutdown of the flame, the thermocouple does not generate any potential difference, therefore, the electromagnet 4 is no longer powered, losing its magnetic coupling with the ferromagnetic element 32 of the rod 21; this leads to the closing of the electric actuator 1, due to the The magnetic force of attraction between 101 and cursor 30.

If an automatic shutdown of the burner is desired, the user decouples the ferromagnetic element 32 from the electromagnet 4, or stops the current path to the electromagnet, by means of a suitable actuating device; The attractive force between provides the closing of the electric actuator 1 .

The closing command can be further obtained through a micro switch on the thermocouple circuit or through a bypass circuit of the electromagnet 4, when the user closes, all or part of the current generated by the thermocouple passes through the bypass circuit, so that the electromagnet 4 The magnetic field is extremely small to allow the pressure to close the passage of the fuel gas.

The embodiment shown in Figures 1 and 2 above, provides that the valve is held in the closed position by a magnetic force generated by at least one ferromagnetic element and at least one permanent magnet.

In the above case, with the attraction of the cursor 30 towards the bottom 101 , the rod 21 translates towards the sleeve 2 and engages the shutter 2 at the mouth of the outlet channel 22 of the fuel gas, closing it.

Construction variants (not shown) provide for use repulsion.

Said configuration (valve closed in resting conditions) remains like this until the user manipulates the electric actuator 1 via the actuating means to switch on the burners of the hob.

In existing electric actuators, a resilient force, usually applied by a compressed coil spring, is used to achieve a "normally closed" condition. Electric actuator 1 according to the above embodiment, characterized in that it achieves the "normally closed" condition by magnetic force and uses it to ensure the outlet passage of the fuel gas when said electric actuator 1 is closed or in a rest condition 22 off.

Replacing springs with magnetics means several advantages, starting with the elimination of components prone to wear.

In fact, springs are components subject to constant mechanical stress, leading to degradation and wear of the elastic elements, which can lead to operational problems.

Furthermore, the spring can jam or stall, compromising the safety of the valve, whereas the magnetic forces that exist between ferromagnets and permanent magnets, due to their nature, do not present this problem.

With reference to Figures 3 and 4, a second possible embodiment of the invention will now be described, illustrated by way of non-limiting example.

Figure 3 shows a section through an electric actuator 1 according to the invention in a closed or rest position.

In this construction variant, the electric actuator 1 advantageously comprises, in addition to the elements already described, a solenoid 33 connected to the wall of said support structure 10 by means of a support element 330 .

Said solenoid 33 is coaxial with the support structure 10 and cooperates with the slider 30 to effect the closing and opening of the electric actuator 1 .

In Figure 3, the electric actuator 1 is in the closed position and the shutter 20 closes the outlet channel 22 for the fuel gas, as previously described (ie by magnetic force).

Figure 4 shows a cross-sectional view of the electric actuator according to the invention in the open or working position, ie the outlet channel 22 for fuel gas communicates with the conduit 23 for fuel gas.

Considering Figures 3 and 4, let us assume that it is desired to turn on the burners of the stove.

Via suitable activation means (not shown), the user activates the power supply to the solenoid 33 , which immediately creates a magnetic field within the support element 33 .

The induced magnetic field exerts a force on the wiper 30 forcing the rod 21 to translate towards the electromagnet 4 , the force generated by the induced magnetic field being greater and in the opposite direction with respect to the attractive magnetic force between the base 101 and the wiper 30 .

The translation of the rod 21 brings the ferromagnetic element 32 into contact with the surface of the electromagnet 4 and opens the outlet channel 22 for the fuel gas.

When the flame is turned on, the power supply to the solenoid 33 is suspended, it no longer produces any type of magnetic field, and the valve opening is ensured by the magnetic force of attraction between the ferromagnetic element 32 and the electromagnet 4 .

During the transition from the user giving the open command to the thermocouple going into operation, the solenoid 33 secures the passage of gas, continuing to power the solenoid for the time interval in question, thereby maintaining the iron through the interaction between the induced magnetic field and the wiper 30. The magnetic element 32 is in contact with the electromagnet 4 .

In case of an accidental shut-off of the flame, the electromagnet 4 is no longer powered by the thermocouple, the magnetic coupling with the ferromagnetic element 32 is lost; the magnetic force of attraction between the base 101 and the wiper 30 leads to the closing of the electric actuator 1 .

If automatic shut-off of the burner is desired, the user activates the electrical power supply to the solenoid 33, but with reversed polarity compared to the opening signal, by means of a suitable actuating device, thereby generating a magnetic field in the opposite direction as before, or blocking The passage of current in the electromagnet 4.

In this case, the magnetic field induces the movement of the cursor 30 towards the sleeve 2 by decoupling the ferromagnetic element 32 from the electromagnet 4 and locking the shutter 20 at the mouth of the outlet channel 22 of the fuel gas by said magnetic force.

Said configuration, ie closing the valve in rest conditions, remains so until the electric actuator 1 is manipulated by the user through the actuating means to switch on the burners of the hob.

The electric actuator 1 according to the invention energizes the switch-on solenoid 33 only during the burner opening and automatic shut-off steps, while for the normal activity of the burner the solenoid 33 is de-energized.

Said solution allows reducing the energy absorption of the electric actuator 1 according to the invention and prevents overheating of the electrical components due to prolonged operation.

Preferably the typical operating voltage of the solenoid 33 is substantially less than or equal to 24V of direct current, and the number of solenoid coils is substantially greater than or equal to 200.

In order to further reduce the heating of the solenoid 33 and increase its service life, it may be advantageous to supply a square wave with a varying duty cycle in order to obtain a maximum displacement force.

The duty cycle or effective duty cycle is the fraction of the time that the entity passes through in the active state and the total time detected. For example, considering a square wave signal, the duty cycle is the ratio of the duration of the active signal to the total cycle of the signal, and is used to indicate the number of cycles Some signals are active.

Furthermore, the electric actuator 1 according to the invention allows switching on and off the burner from a remote location, since the actuation commands performed by the user are of electrical and non-mechanical nature.

Figure 5 shows a sectional view of an electric actuator according to another possible implementation variant of the invention;

In Fig. 5, the electric actuator 1 is in the closed position and the shutter 20 closes the outlet channel 22 for the fuel gas.

In this construction variant, the pressure is of elastic nature and the electric actuator 1 is held in the normally closed position by elastic loading means, advantageously compressing the helical spring 200 .

In fact, by looking at the drawings, it can be understood that the spring 200 bears against the shutter 20 while keeping the outlet passage 22 of the fuel gas closed.

Compared to the previous embodiment, the magnetic force (keeping the outlet channel of the fuel gas closed) has been replaced by the elastic force imparted by said spring 200 .

In this construction variant, the cursor 210 is provided to contain ferromagnetic elements.

Said slider 210 cooperates with the base 102 , also made of ferromagnetic material, placed inside the cavity 100 .

Regarding the above description, let us assume that it is desired to turn on the burners of the stove.

Via suitable actuating means (not shown), the user activates the power supply to the solenoid 33, generating a magnetic field which induces translation of the wiper 210 towards the electromagnet 4, said induced magnetic field producing a greater force and relative to a compression helical The elastic forces of the spring 200 on the shutter 20 are in opposite directions.

The shutter 20 is moved away from said outlet channel 22 of the fuel gas, thus allowing gas to enter from the outlet channel 22 and reach the burner.

Translation of the rod 21 brings the ferromagnetic element 32 into contact with the surface of the electromagnet 4 .

When the ferromagnetic element 32 and the electromagnet 4 are in contact and the electromagnet 4 is powered by a thermocouple (or flame sensor) exposed to the flame, it is intuitive that the ferromagnetic element 32 present on the rod 21 and the electromagnet The magnetic force between the irons 4 is greater than the elastic force produced by the compressed coil spring 200 .

The shutdown command is generally obtained by the disappearance of the current produced by the thermocouple.

Alternatively, the variant of FIG. 5 could provide only the slider 210 , eliminating the bottom 102 , provided that said slider 210 is made of magnetic material in order to be able to be controlled by the solenoid 33 .

In short, the electric actuator 1 according to the invention comprises at least a compression/tension force, which achieves a normally-off condition, blocking the passage of fuel gas to the burner.

According to a construction variant, said compression/tension force may advantageously be of elastic or magnetic nature.

When the compression/tension force is of elastic nature, the electric actuator 1 comprises at least one elastic means, such as a compression spring, and in the case of compression/tension force, the electric actuator comprises at least one ferromagnetic element and at least one permanent magnet , they are properly installed and cooperate with each other.

In general, said compression/tension force is liable to be exceeded by the command force applied to open said outlet channel 22 and said anchoring force between ferromagnetic element 32 and electromagnet 4 .

With regard to the opening and closing commands of the electric actuator 1 according to the invention, it can advantageously be controlled manually or electrically.

In the case of manual opening and closing, the user translates the valve stem 21 by appropriate controls, bringing the ferromagnetic element 32 into contact with the electromagnet 32, while in the case of closing the user decouples said element.

The electronically controlled opening and closing takes place through the interaction between a magnetic field sensitive wiper and an electromagnet, advantageously a solenoid 33 .

If the slider comprises a permanent magnet, the opening and closing commands can be applied by the solenoid 33 , in particular by reversal of its magnetic poles.

In the case where the slider comprises a ferromagnetic element, the opening of the electric actuator 1 takes place via a solenoid 33 that pushes the slider towards the bottom 102, while the closing command can be substantially given by a thermocouple The disappearance of the generated current is obtained.

This can be achieved in at least two ways:

- Via a single normally closed switch on the thermocouple circuit which the user opens to cut off the current, provided the range is equipped with suitable certified electronics.

- A bypass circuit through the coil of the electromagnet normally open, closed by the user, on which substantially all the current passing in the coil is diverted, significantly reducing its magnetic field.

Nothing prevents also applying these switch-off modes to variants where the cursor is a permanent magnet.

Fig. 6 shows an electric actuator 1 according to the invention with an interfering membrane 230 placed in the conduit 23 of the fuel gas close to the rod 21 to prevent said fuel gas from flowing into the same electric actuator.

Advantageously, the interference membrane 230 is suitable for all above-mentioned implementation variants.

Figure 7 compares two cross-sectional views of an electric actuator according to the invention in an open condition and a closed condition.

In the figures, for ease of reading and understanding, the reference numerals of the various components are not provided, and the terms and concepts expressed advantageously in FIG. 7 extend to all previously shown and described embodiments.

Then, with reference to the reference numerals of Figures 1, 2, 3, 4, 5 and 6, a terminology explanation for Figure 7 is provided below, where:

-D is the outer diameter of the valve body (or its largest dimension if it is a non-cylindrical part);

-X is the instantaneous position of the reference (e.g. center of gravity) of the element 30, 210 relative to a reference integral with the valve body (e.g. the bottom 101) between a minimum value Xmin (corresponding to said outlet channel 22 being closed) and a maximum value Xmax (corresponding to the opening of the outlet channel 22).

- C is the maximum stroke of the translating element 20, 21, 30, 32, 210, constrained between them, and C=Xmax-Xmin;

- FF is the mutual attractive force between the element 30 and the base 101, varying according to the instantaneous position X, and thus _FF = _{FF_MAX} when X = _Xmin and _{FF = FF_min when} X = Xmax, where obviously F _{F_MAX} is the maximum attraction, and F _{F_min} is the minimum attraction;

- The command force F _S is the resultant force of the forces generated by the solenoid 33 on the element 30 in the "x" direction, that is to say, said command force F _S is the resultant of the forces generated by the solenoid 33 acting on the slider 30 , whose direction and strength depend on the signal and strength of the current flowing through the solenoid coil;

- The anchoring force F _P is the mutual attractive force between the element 32 and the electromagnet 4 , which arises when the flame is lit and the thermocouple is activated; it varies according to the instantaneous position X.

Said _force FF is a compression/tension force which operates the safety closing of said electric actuator 1 and is liable to be exceeded by the command force _FS applied to open said outlet channel 22 and said anchoring force FP. In addition, the anchoring force F _P is as follows:

-F _P ＝0, the flame is shut off now (the electromagnet 4 has no power supply);

- F _P ≠ 0, when the flame is on (electromagnet 4 powered), and F _P = F _{P_MAX} when X = XMAX, F _P = F _{P_min} when X = Xmin, where obviously F _{P_MAX} is the maximum anchoring force, And F _{P_min} is the minimum anchoring force.

In a preferred embodiment, the electric actuator according to the invention is characterized in that all of the following conditions exist simultaneously (the module of force must be taken into account):

-D≤20[mm];

-0,08D<C<0,4D;

-F _{P_MAX} >F _{F_min} ;

-F _{F_MAX} >F _{P_min} ;

-F _{S_MAX(+)} >F _{F_MAX} ;

-(F _{S_MAX(-)} +F _{F_min} )>F _{P_MAX} .

In particular, once the geometry is fixed, the magnitude and direction of the current equal to _F can be considered to be approximately constant (as the position X varies), and its is equal to F _{S_MAX(+)} (opening command of outlet channel 22 ), which is equal to F _{S_MAX(−)} (closing command of outlet channel 22 ) when said resultant force acts in the negative direction of the x-axis.

Also corresponding to the signal of the current supplying the solenoid 33 , F _S can take the positive value F _{S_MAX(+)} and the negative value F _{S_MAX(-)} .

Figure 8 shows a summary table of parameters and possible operating configurations of an electric actuator according to the invention.

The table shows:

- Status: Indicates the status of the electric actuator 1 and the fuel gas burner:

- "at rest": the electric actuator 1 is in a normally closed position and the burner is switched off;

- "transition": the electric actuator is switched from the closed position to the open position, or vice versa, the burner can be switched on if commanded to be switched on, and can be switched off if commanded to switch off;

- "open": the electric actuator 1 is in the open position and the burner is switched on;

- "OFF": the electric actuator 1 is in the normally closed position and the burner is switched off.

- Flame: Indicates the presence of a flame for the fuel gas burner (on for presence of flame; off for absence of flame).

- Solenoid: Indicates power supply to the solenoid, ON (+) is positive power supply to solenoid 33, OFF (-) is negative power supply to solenoid 33.

Preferably, the command ON (+) provides the opening of the electric actuator 1 and the command OFF (-) provides the closing of the electric actuator 1 .

States are interpreted as various operating conditions of the burner controlled by the electric actuator 1 of the present invention, where:

- "regular opening" indicates the opening of the burner and the opening of the electric actuator 1;

- "automatic shutdown" indicates the shutdown of said burner and the shutdown of said electric actuator 1;

- "Unexpected shutdown" indicates the shutdown of said burner and the shutdown of said electric actuator 1;

- "Attempt to open" indicates a failed opening attempt of the burner and a closing of the electric actuator 1 .

In short, the effective force of the electric actuator 1 can be summarized as follows:

_-Valve closing: only FF exists, and it executes normally closed;

- valve open: F _F and F _P both exist, where F _P > F _F , F _P keeps the valve open;

_-FF , _FP and _FS are present in the transition.

Obviously, combinations of the above-mentioned variants in various ways can lead to further variants without departing from the scope of the present invention, and many embodiments and applications are possible.

The electric actuator according to the invention is useful, for example, for the supply of premix burners for stoves, both of the atmospheric type and of the blowing type, as documented in documents AN2014A000130, AN2014A000176, AN2015A000041, AN2015A00042, AN2015A000060, AN2015A000061 and 10201510000184 those described.

By "premix burner" it means a burner in which the supply of primary air is sufficient for complete combustion without the need for secondary air over the flame.

By "draft burner" it means a burner in which the primary air to take part in the combustion is not drawn by the Venturi effect, but is fed into the same burner by a fan in precisely controlled quantities. Therefore, in such burners, primary air enters through calibrated orifices, and in many cases, as appropriate, once the air is supplied/intercepted, it is fed or intercepted at the same time.

Figures 9a and 9b show two examples of gas valves 25 suitable for blowing burners, in which an electric actuator (not shown in detail) according to the invention can be used.

The two figures with 21 show a rod in which one or more shutters 20 are bound, which cut off the passage of gas and air from the respective distribution ducts 23 and 24 towards the outlet channel 22 to the burner.

In particular, Figure 9a shows two valves 25, in each of which a corresponding single shutter 20 intercepts two concentric air and gas orifices, while in Figure 9b the rod 21 carries two shutters 20, one for intercepting one for gas, and another for intercepting air.

Claims (18)

1. An electric actuator (1) for gas hobs etc., piloted by actuating means, comprising: at least one safety electromagnet (4) forming part of a pilot stabilizer; at least one cut-off means for fuel gas (2), which is substantially a bushing with an outlet channel (22) and a conduit (23) for fuel gas, at least one safety shutter (20) on which a push/pull _force (FF ) acts to make said outlet passageway (22) safety closing; at least one service shutter (20); support structure (10) with a cavity (100) in which a rod (21) is placed slidingly, cooperating with said safety electromagnet (4) At least one ferromagnetic element (32) and said shutter (20) cooperating with the fuel gas shut-off device (2) are bound by it, wherein said safety shutter (20) and said service shutter (20) coincide in the same shutter (20); said ferromagnetic element (32) is _anchored to said safety solenoid (4), It is characterized by: - said compression/tension force (FF ) is of magnetic nature, which is easily exceeded by the command force (FS ) and said anchoring force ( _{F P )} applied for the opening of said outlet channel (22). 2. Electric actuator (1) according to the previous claim, wherein said magnetic force is composed of a vernier (30) placed on said rod (21) and a bottom placed in said cavity (100) The magnetic fit of (101) is given. 3. The electric actuator (1) according to the preceding claim, wherein the instantaneous position (X) of the cursor (30) relative to the bottom (101) corresponds to the closure of the outlet channel (22) varies between a minimum value (Xmin) and a maximum value (Xmax) corresponding to the opening of said outlet channel (22), characterized by: - The mutual attractive _force (FF) between said cursor (30) and said base (101) varies according to the instantaneous position (X), and thus when the instantaneous position is at a minimum (X=Xmin) said The force is the maximum value (F _F =F _{F_MAX} ); and when the instantaneous position is the maximum value (X=Xmax), the force is the minimum value (F _F =F _{F_min} ); - The anchoring force (F _P ) between the ferromagnetic element (32) and the electromagnet (4) varies according to the instantaneous position (X), and thus said force when the instantaneous position is at its maximum value (X=X _MAX ) is the maximum value (F _P =F _{P_MAX} ), while said force is the minimum value (F _P =F _{P_min} ) when the instantaneous position is the minimum value (X=Xmin); and is characterized by: - said maximum anchoring force (F _P =F _{P_MAX} ) is greater than the minimum mutual attraction force (F _F =F _{F_min} ) between said vernier ( 30 ) and said bottom ( 101 ); - said maximum mutual attractive force (F _F = _{FF_max} ) between said slider (30) and said bottom (101 ) is greater than said minimum anchoring force (F _P =F _{P_min} ). 4. Electric actuator (1) according to claim 2, wherein said base (101) comprises a ferromagnetic element and said slider (30) comprises a permanent magnet. 5. The electric actuator (1) according to claim 2, wherein said base (101) comprises a permanent magnet and said slider (30) comprises a ferromagnetic element. 6. The electric actuator (1) according to claim 2, wherein the base (101) comprises a permanent magnet and the slider (30) comprises a permanent magnet. 7. Electric actuator (1) according to the preceding claim, wherein for the opening of the outlet channel (22), ie the opening of the burner, by manual or automatic action, the ferromagnetic element (32) of the rod (21) ) is in contact with the safety solenoid (4) and remains at least integral until said safety solenoid (4) is activated after switching on the burner. 8. Electric actuator (1) according to the preceding claim, wherein for the opening or automatic closing of the outlet channel (22), ie the automatic opening and closing of the burner, by means of said actuating means, the user manually Coupling and decoupling said ferromagnetic element (32) of said rod (21) and said electromagnet (4). 9. Electric actuator (1) according to the preceding claim, further comprising at least one solenoid means (33) cooperating with said vernier (30) by means of a suitable magnetic 33) Supply electric energy to realize the opening or automatic closing of the outlet channel (22), that is, the automatic opening or closing of the burner. 10. Electric actuator (1) according to claim 9, wherein said command force (Fs) is the resultant force of the forces generated by the solenoid (33) acting on the vernier (30), the direction and strength of which depend on Depending on the signal and strength of the current flowing through the solenoid (33) coil; said command force (Fs) is characterized by: - in order to command the opening of said exit channel (22), said command force (F _S =F _{S_MAX(+)} ) is greater than said maximum mutual attractive force (F _F =F _{F_MAX} ); - In order to command said exit channel (22) to close, the sum of the command force (F _S =F _{S_MAX(-)} ) and the minimum mutual attraction force (F _F =F _{F_min} ) is greater than the maximum anchoring force (F _P =F _{P_MAX} ). 11. Electric actuator (1) according to claim 10, wherein for the opening of the outlet channel (22), i.e. the opening of the burner, by means of said actuating means, the user activates a switch to said solenoid ( 33) power supply, the solenoid remains energized until the safety electromagnet (4) is activated after the burner is switched on. 12. Electric actuator (1) according to claim 9, wherein said vernier (30) is a permanent magnet and is an automatic closing of the outlet channel (22), ie automatic shut-off, by said actuation means, the user activates the power supply to said solenoid (33), flipping the Polarity of solenoid (33). 13. The electric actuator (1 ) according to any one of claims 9 to 12, wherein the solenoid (33) can be supplied with a square wave having a duty cycle. 14. Electric actuator (1) according to claim 8 or 9, wherein said cursor (30) is a ferromagnetic element, by means of actuation, the user cuts off the power supply to the safety electromagnet (4) to Automatically closes the outlet channel (22), ie shuts off automatically. 15. The electric actuator (1 ) according to claim 14, wherein said cutting off the supply of electrical energy to the electromagnet (4) occurs by closing a bypass circuit of the electromagnet (4). 16. Electric actuator (1) according to claim 14, wherein said cutting off the supply of electrical energy to the electromagnet (4) takes place via a normally closed microswitch on the circuit of the safety electromagnet (4), the user Open it to cut off the current. 17. The electric actuator (1) according to claims 1 to 16, characterized in that it further comprises an interference membrane (230) placed on said rod inside said solenoid (33) of fuel gas (21) NEARBY. 18. A stove with a blower burner using the electric actuator (1) according to claims 1 to 17.