WO2008141916A2

WO2008141916A2 - Safety gas cock for a dual burner

Info

Publication number: WO2008141916A2
Application number: PCT/EP2008/055513
Authority: WO
Inventors: Giancarlo Defendi; Carlo Paesani
Original assignee: Defendi Italy S.R.L.
Priority date: 2007-05-17
Filing date: 2008-05-06
Publication date: 2008-11-27
Also published as: CN101680661A; WO2008141916A3; ITVE20070031A1; ES2379029A1; ES2379029B1; CN101680661B

Abstract

A safety gas cock for a dual burner, provided with one central flame ring (6) and at least one outer flame ring (8, 8') concentric with said central ring, said cock being of the type comprising two outlets (12, 14) which independently feed said central ring (6) and said outer ring (8, 8'), and with an adjustment cone (29) operable by a rotary knob (32) to adjust gas distribution either towards only said central ring (6) or towards said central ring (6) and towards said outer ring (8, 8') simultaneously, characterised in that said adjustment cone (29) defines a central position in which both said outlets (12, 14) are closed, and from which central position it can be rotated in one direction to adjust the gas flow through a single outlet (12) between a maximum value and a minimum value, and in the other direction to adjust the gas flow through both outlets (12, 14) between a maximum value and a minimum value.

Description

SAFETY GAS COCK FOR A DUAL BURNER

The present invention relates to a safety gas cock for a dual burner. Dual burners are known. These are concentric burners with a central body or inner burner provided on its periphery with an inner flame ring, and an annular body or outer burner provided on its perimeter with one or two concentric flame rings.

In the present description reference is made to a burner with its outer annular body provided with two flame rings, however that stated is also valid in the case of a burner with its outer body provided with a single flame ring. In known dual burners a first injector is associated with the central body to feed gas to a first venturi, in which a gas-air mixture is formed to feed the inner flame ring, while a second injector is associated with the annular body to feed gas to a second venturi, in which a gas-air mixture is formed to feed the outer flame rings. The two Venturis are fed from two different outlets of a single cock, by which the user controls the different modes of burner operation, depending on requirements. These operating modes are such that either the outer and inner bodies of the burner can be both fed to generate flame rings adjustable from a minimum to a maximum, or only the inner body can be fed to generate just the inner flame ring, adjustable from a minimum to a maximum. In either mode of operation the inner flame ring is always fed, hence the safety device thermocouple is installed in proximity to the burner inner body.

In these known burners the different modes of operation are always chosen and adjusted by a single knob, which as it rotates controls the adjustment cone of the double-outlet cock. In a first type of cock for a dual burner, when the knob is in the 0° position the burner is closed, while with the knob in the 90° position both the two burner bodies (outer and inner) are fed at maximum flow, then in passing from 90° to about 140° there is a progressive reduction in flow through the two burner bodies until the minimum value is reached, then from 140° to 180° the feed to the outer body is interrupted and the flow through the inner body is increased to its maximum value, and finally after passing the 180° position the gas flow through just the inner body decreases until its minimum value, at the knob stop position. In a second type of cock for a dual burner, when the knob is in the 0° position the burner is closed, while with the knob in the 90° position only the inner burner body fed at maximum flow, then from 90° to about 140° its flow is reduced until the minimum value is reached, then from 140° to 180° both burner bodies are fed at its maximum flow at 180°, and finally the gas flow through both burner bodies decreases until its minimum value, at the knob stop position.

As will be apparent, both the known types of dual burner cocks are difficult to adjust by the user because the adjustment is not immediate and intuitive. In addition to this drawback, both the known types of dual burner cock present another much more important drawback, in that in passing from the knob position corresponding to two burners fed, to the knob position corresponding to only the inner burner fed, there is no well defined position in which gas feed to the outer burner is reliably interrupted. It follows that if the outlet for the gas feed to the outer burner is not completely closed, this state may not be detected by the safety device because the inner ring is fed and the thermocouple is activated. Under these circumstances, the quantity of gas-air mixture leaving the outer body is too small to cause inter-ignition between the two burners with the flames of the inner burner, consequently unburnt gas escapes to the atmosphere. WO2005/003610 teaches this problem and solves it by preventing the user from being able to move the knob into this critical position. In particular, this document suggests applying to the cock control rod of the knob a spring able to interact with a projection provided on the cock body. When the spring reaches this projection during cock operation, the user has to apply a greater force to rotate the knob beyond the critical area.

However this solution cannot be considered satisfactory both because the user perceives this force as imperfect operation of the cock and because the problems due to lack of immediate and instinctive perception of its operation are not eliminated. An object of the invention is to eliminate these drawbacks by providing a safety cock for a dual burner in which escape of unburnt gas from the outer annular body is not possible when the burner operates with only the central flame ring at its minimum.

Another object of the invention is to provide a cock in which the adjustment operation by the user is simple and instinctive, and without giving rise to the sensation of maloperation.

These and other objects which will be apparent from the ensuing description are attained according to the invention by a safety gas cock for a dual burner, as described in claim 1 . A preferred embodiment of the present invention is described in detail hereinafter with reference to the accompanying drawing, in which: Figure 1 is a partially sectioned perspective view of a cock according to the invention, Figure 2 is a section therethrough taken perpendicular to the axis of rotation of the cock, Figures 3a - 3c are schematic front views of three different positions of the control cock for feeding both the central body and the outer body of the burner, the plan views showing the corresponding flame ring conditions, and

Figures 4a - 4c are schematic front views of three different positions of the control cock for feeding just the central body the burner, the plan views showing the corresponding flame ring conditions. As can be seen from the figures, the safety cock of the invention is intended to feed a traditional dual burner, i.e. a burner comprising a central body 2 or inner burner and an annular body 4 or outer burner, concentric to the first.

The inner burner 2 is provided with one flame ring 6, while the outer burner 4 is provided with two flame rings 8, 8', which emerge from its outer periphery and from its inner periphery, although in different burner types a single flame ring can be provided emerging from only the outer periphery of the outer burner 4.

Both the inner burner 2 and outer burner 4 are fed by the cock of the invention, which comprises a body 9 with a gas inlet 10 for connection to the distribution mains, and two gas outlets 12 and 14 for independent feed to the two burners 2 and 4. The inlet 10 is connected via a conduit 16 to a chamber 18, closed by a valving element 20 associated in traditional manner with an electromagnet 22. This is maintained in the closed state by a spring 24, but can be withdrawn therefrom to open said chamber 18 and connect it to a downstream chamber 26. In the same manner as most cocks with a thermocouple safety device, the electromagnet 22 is activated, to maintain the chamber 18 open against the reaction of the spring 24, by an electric current generated by a thermocouple 28 positioned in proximity to the inner burner 2 and sensitive to the flames 6 emerging from this latter.

The downstream chamber 26 communicates with the inner cavity of an adjustment cone 29, rigid with a rod 30 to which an adjustment knob 32 is applied.

This rod 32 and the cone 29 are also movable in an axial direction as in the case of traditional safety cocks for burners, in order to manually control the temporary movement of the electromagnet 22, causing the chamber 18 to open, until the thermocouple 28 generates the current necessary to maintain the electromagnet 22 in its open state.

The side wall of the adjustment cone 29 also comprises a pair of apertures 34 and 36, which as the angular position of the cone varies establish in traditional manner the communication between its inner cavity and apertures 38 and 40 provided in the cone seat and connected to the two gas outlets 12 and 14.

The angular width of the apertures 34, 36, 38 and 40 is such as to enable the gas flow to be regulated in accordance with the burner design data, however this forms part of the knowledge of the expert of the art and does not require further explanation. In addition the two outlets 12 and 14 are provided with traditional bypasses 42, 44 which ensure gas feed at minimum flow for the two burners 2 and 4, in accordance with the angular position of the knob 32 and of the cone 29 rigid with it.

The safety cock of the invention operates in the following manner: when the knob 32 is in its central position, both the outlets 12 and 14 are closed and the electromagnet 22 maintains communication between the upstream chamber of the valving element 20 and the downstream chamber 26 closed (see Figures 3a and 4a).

To feed both the burners 2 and 4 the user rotates the knob 32 clockwise through 90° while pressing it axially. This rotation of the knob 32 (see Figure 3b) causes the cone 29 to open the two outlets 12 and 14 at maximum flow, while its axial movement causes the valving element 20 to open manually and powers the ignition plug 46. This generates the spark and ignites the gas-air mixture feeding the central burner 2, to generate the inner flame ring 6 which then generates the outer flame rings 8, 8' by inter-ignition.

At the same time, the flames of the inner ring 6 heat the thermocouple 28, which generates the current necessary to maintain the electromagnet attracting and consequently the valving element open, even after releasing the knob 32. The flames of both the inner burner 2 and outer burner 4 can then be adjusted in traditional manner by rotating the knob from the 90° position onwards until it encounters a stop position (Figure 3c) at which both the burners are fed at a minimum via the respective by-passes 42, 44.

If the user wishes to have only the inner burner 2 ignited instead of both burners 2 and 4, the same aforedescribed operations have to be carried out, but rotating the knob 32 anti-clockwise instead of clockwise. In this manner the action of the apertures 34 and 36 provided in the adjustment cone 29 and of the apertures 38 and 40 provided in its seat in the cock body causes opening of just the outlet 12 feeding the inner burner 2, making it possible to adjust it from maximum flow (see Figure 4b) to minimum flow (see Figure 4c) according to requirements.

Essentially the cock of the invention eliminates all the drawbacks encountered in known dual burner cocks, in that it excludes any possibility of a critical position existing in which unburnt gas escapes from the outer burner, while at the same time the flames can be adjusted smoothly and instinctively, with rotation of the knob 32 in one direction to feed both the flame rings, and in the opposite direction to feed just the inner ring.

Moreover according to the invention the two positions of the knob 32 at minimum and maximum gas feed to one or both the burners is inverted, i.e. rotating the knob to 90° clockwise or anticlockwise corresponds to minimum feed, whereas further knob rotation in one or other direction until it stops corresponds to maximum feed.

Claims

C L A I M S

1 . A safety gas cock for a dual burner, provided with one central flame ring (6) and at least one outer flame ring (8, 8') concentric with said central ring, said cock being of the type comprising two outlets (12, 14) which independently feed said central ring (6) and said outer ring (8, 8'), and with an adjustment cone (29) operable by a rotary knob (32) to adjust gas distribution either towards only said central ring (6) or towards said central ring (6) and towards said outer ring (8, 8') simultaneously, characterised in that said adjustment cone (29) defines a central position in which both said outlets (12, 14) are closed, and from which central position it can be rotated in one direction to adjust the gas flow through a single outlet (12) between a maximum value and a minimum value, and in the other direction to adjust the gas flow through both outlets (12, 14) between a maximum value and a minimum value.

2. A cock as claimed in claim 1 , characterised in that the two positions of said adjustment cone (29), i.e. those rotated through about 90° from the central closed position in the two directions, correspond to maximum feed through a single outlet (12) and maximum feed through both outlets (12, 14) respectively, while further rotation of said adjustment cone (29) in the two directions from the position at about 90° to a stop position corresponds to gas feed adjustment from maximum to minimum.

3. A cock as claimed in claim 1 , characterised in that the two positions of said adjustment cone (29), i.e. those rotated through about 90° from the central closed position in the two directions, correspond to minimum feed through a single outlet (12) and minimum feed through both outlets (12, 14) respectively, while further rotation of said adjustment cone (29) in the two directions from the position at about 90° to a stop position corresponds to gas feed adjustment from minimum to maximum.

4. A cock as claimed in one or more of claim 1 to 3, characterised in that a minimum flow by-pass (42, 44) is associated with each of the two outlets.