DEVICE FOR REGULATING THE AIR/GAS MIXTURE SUPPLIED TO BURNER APPLIANCES, IN PARTICULAR FOR BURNERS OF DECORATIVE FIRES

Abstract

A device for regulating the air/gas mixture supplied to a gas burner appliance of a decorative fire is provided. The device includes a duct for supplying the air/gas fuel mixture to the burner and a choke of the flow of primary air taken into the duct and adapted to be mixed with the flow of gas or the flow of the air/gas mixture, in which heat-sensitive actuator acting directly on the choke is provided so that the choking of the flow is regulated automatically as a function of the heat level reached in the heat-sensitive actuator.

Description

TECHNICAL FIELD

The present invention relates to a device for regulating the air/gas mixture supplied to a burner appliance, in particular for burners of decorative fires, having the characteristic features set out in the preamble of the main claim.

TECHNOLOGICAL BACKGROUND

The invention is of particular, but not exclusive, application in the particular sector of gas burner appliances designed to generate purely decorative flames in fires.

In these applications, it is known that when the burner is ignited the colour of the flames generated is normally mainly blue; this colouring is characteristic of combustion in surplus air and is also connected with the greater density of the air due to the low temperatures of the environment surrounding the burner, and is adapted to vary as the fire gradually heats up until a yellow colouring, adapted to simulate the typical combustion of a wood fire as well as possible, is achieved.

A particular need arises in display areas for these fires (also known as the showrooms of production and sales areas), where it would be desirable to be able immediately to show, on ignition of the fire, the best quality of the flames generated so that the typical, particularly attractive and highly decorative, yellow colouring of the fire can be appreciated. However, in these display areas, where there are normally relatively low ambient temperatures, it is not possible to obtain the desired yellow colouring of the flames which is typical of the particular decorative nature of the fire rapidly enough during demonstrations of the product on display.

DESCRIPTION OF THE INVENTION

A main object of the invention is to provide a device for regulating the supply of air/gas mixture in gas burner appliances which is structurally and functionally designed to remedy the drawbacks of known solutions, i.e. the need rapidly to obtain, on ignition of the fire, flames of a decorative impact similar to those which can normally be obtained only after a certain period of regular operation of the fire.

This object is achieved by the invention by means of a device for regulating the air/gas mixture embodied in accordance with the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristic features and advantages of the invention are set out in the following detailed description of some preferred embodiments thereof, shown by way of non-limiting example, and made with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a first embodiment of a device of the invention;

FIGS. 2 and 3 are front elevations of the device of FIG. 1 in two different operating conditions;

FIG. 4 is a perspective view of a second embodiment of the device of the invention;

FIGS. 5 and 6 are front elevations of the device of FIG. 4 in two different operating conditions;

FIGS. 7 and 8 are lateral elevations of the device of FIG. 4 in the corresponding operating conditions of FIGS. 5 and 6;

FIGS. 9 and 10 are lateral elevations, partly in section, of a third embodiment of the device of the invention in two different operating conditions.

PREFERRED EMBODIMENTS OF THE INVENTION

With reference first to FIGS. 1 to 3, a first embodiment of a device for regulating the air/gas mixture supplied to a burner appliance 2, in accordance with the invention, is shown overall by 1.

The gas burner 2 is advantageously adapted to be located in a fire of decorative type, in which flames adapted to simulate the typical combustion of a wood fire are generated by combustion of the gas.

The device 1 comprises a supply duct 3 for the air/gas mixture connected to the body 2a of the burner in which the outlet nozzles for the fuel mixture are provided. The gas is typically injected into one end 3a of the duct so that it can be mixed with the primary air taken from the surrounding environment and in particular taken in by the vacuum generated by the gas jet pulse at the mouth of the duct at the end 3a.

According to a main characteristic feature of the invention, the duct 3 is provided, downstream of the end 3a with respect to the direction of flow of the mixture to the burner 2, with a transverse through opening 4 in the wall of the duct. This auxiliary ventilation opening is associated with a choke means comprising a pin shutter member 5 whose displacement through the opening is controlled by heat-sensitive actuator means, as will be described in detail below.

The actuator means comprise a bimetallic plate member 6 formed by a pair of strips 6a, 6b of respective metals having different coefficients of thermal expansion. The plate 6 is connected at its end 6c to the duct 3 and is provided with the pin shutter 5 in an intermediate section, the point of fastening to the duct being selected such that the pin 5 may slide in a limited manner in the through opening 4. The plate is dimensioned, moreover, so that, as a function of the level of heat reached in the strips 6a, 6b, it is deformed as a result of the different thermal expansions of the metals, so that it can be displaced from a first position in which it extends to surround the duct with the pin 5 disposed in the duct (FIG. 2) and a second position in which it is remote from the duct with the pin 5 in the position extracted from the duct (FIG. 3). In particular, the position of FIG. 2 is assumed by the plate at ambient temperature and, as the level of heat achieved in the plate gradually increases following ignition of the burner, the plate is gradually deformed until it reaches the position of FIG. 2, by way of example when the temperature of the plate is preferably approximately 40° C. or more.

In the position of FIG. 2, the pin shutter 5, as it is fully disposed in the duct (via the opening 4), is able to choke the flow supplied to the duct and to intercept the auxiliary ventilation opening 4. In this condition, the oxygen content in the flow of primary air adapted to be mixed with the gas is therefore reduced with the result that the combustion obtained in the burner, lacking oxygen, is such as to generate flames of the typical yellow colour simulating the combustion flames of a wood fire as well as possible. In this way, therefore, with the fire off, and the plate in the position of FIG. 1 which it assumes at ambient temperature, flames of yellow colour instead of the blue colour that would be obtained without the assistance of the choke means can be immediately obtained when the burner is ignited. It is therefore possible to obtain, in very short times after ignition, flames of yellow colour with the best decorative impact that can be achieved. Then, as the fire gradually heats up, and the threshold of the above-mentioned heat level is reached in the bimetallic plate, the latter is gradually deformed until it assumes the configuration of FIG. 3 in which the shutter no longer performs any function of choking of the flow and primary air may also be taken in through the ventilation opening for mixing with the gas. The above-mentioned choke means which are automatically controlled by the heat-sensitive actuator, therefore make it possible rapidly to appreciate the decorative effect of the flames in the fire even at a relatively low ambient temperature; this is particularly valuable during demonstration activities in display areas for fires.

In FIGS. 4 to 8 a second embodiment of the device of the invention is shown by 10, in which details similar to those of the previous embodiment bear the same reference numerals.

In this embodiment, the duct 3 is provided with a pair of diametrically opposed through openings 11a, 11b which are associated with respective flanges 12a, 12b of a U-shaped choke member 12, with the flanges extending uniformly from a connecting section 12c. The choke member is adapted to be detachably connected to the duct, with the flanges disposed in a position facing the corresponding openings. It is also provided for at least the flanges 12a, 12b to be made from a bimetallic material by coupling of a pair of strips of respective metals having different coefficients of thermal expansion, in a similar manner to that described in the previous embodiment. This embodiment enables the flanges 12a, 12b to be deformed when a predetermined heat level is reached, and to assume a configuration in which the flanges are mutually spaced in order externally to open at least part of the through openings 11a, 11b with the result that primary air is taken into the duct 3.

In operation, the configuration of FIG. 5 is the configuration assumed at ambient temperature, in which the flanges 12a, 12b are disposed to intercept the through openings 11a, 11b so as to enable combustion, lacking oxygen, when the burner is ignited, thus instantaneously obtaining the best decorative effect, with a typical yellow flame, in the fire.

When the predetermined heat threshold for the dimensions of the bimetallic choke is reached, its flanges are deformed and displaced into the configuration of FIG. 6, in which, as a result of their movement apart, the openings 11a, 11b allow air to be taken in and to pass into the duct as a result of the vacuum caused in the duct, thus increasing the oxygen content and enabling full combustion in the burner.

In FIGS. 9 and 10, in which details similar to those of the previous embodiments bear the same reference numerals, a third embodiment of the device of the invention is shown by 20.

In this embodiment, a bimetallic plate 22 disposed inside the duct so that it can perform the function of a choke means is disposed in the section of the duct 3 downstream of the end 3a where the axial injection of primary air takes place via a nozzle 21 and where the primary air is taken in as a result of the vacuum caused by the flow of gas injected. In particular, the plate 22 is connected to the duct at an end 22a and is made from a pair of mutually superimposed metal strips having different coefficients of thermal expansion which extend inside the duct and can be displaced, as a function of the heat level reached in the plate, between the configurations shown in FIGS. 9 and 10 respectively.

The configuration of FIG. 9 is the configuration assumed at ambient temperature in which the plate is immersed in the axial flow of the duct, so as to choke the flow supplied and thus enable combustion, lacking oxygen, when the burner is ignited, thus instantaneously obtaining the best decorative effect, with a typical yellow flame, in the fire.

When the predetermined heat level for the dimensions of the bimetallic choke is reached, the plate 22 is deformed and displaced into the configuration of FIG. 10 in a position backing onto the inner wall of the duct 3 without performing any significant action to disturb or choke the flow of gas and thus enabling a full flow to the burner.

It will be appreciated in this embodiment that the plate 22 itself acts a choke member of the flow supplied in the duct 3.

The above-mentioned plate may also be disposed in the section of the duct 3 forming the convergent part of a Venturi tube provided for the mixing of the air/gas of the fuel supplied to the burner.

The invention thus achieves the objects as set out and achieves the advantages discussed with respect to known solutions.

Claims

1. A device for regulating an air/gas mixture supplied to a gas burner appliance of a decorative fire, comprising a duct for supplying the air/gas fuel mixture to the burner and a choke of a flow of primary air taken into the duct and adapted to be mixed with a flow of gas or a flow of the air/gas mixture, the device comprising a heat-sensitive actuator acting directly on the choke so that the choking of the flow is regulated automatically as a function of a heat level reached in the heat-sensitive actuator.

2. A device according to claim 1, wherein the heat-sensitive actuator is of the type with a bimetallic plate made from respective metals having different coefficients of thermal expansion.

3. A device according to claim 2, wherein the choke comprises a choke member of the flow connected to the plate so as to be automatically displaced from and to a position choking the duct as a function of the temperature reached in the plate following ignition of the burner.

4. A device according to claim 2, wherein the choke comprises at least one shutter member associated with at least one respective through opening through the duct adapted selectively to enable the intake of primary air into the duct, the shutter member being controlled in operation by the bimetallic plate actuator.

5. A device according to claim 2, wherein the bimetallic plate forms the choke member of the flow.

6. A device according to claim 5, wherein the plate is disposed inside the duct (3).

7. A device according to claim 5, wherein the plate is connected at one end to the inner wall of the duct and can be displaced between a first position in which, at ambient temperature, it is disposed in the position of maximum choking of the flow supplied through the duct so as to reduce the quantity of primary air of the air/gas mixture, and a second position in which, at a predetermined temperature level, the plate is disposed in the position of minimum choking of the flow.

8. A device according to claim 7, wherein the temperature level is selected to be equal to or more than 40° C.