GB2183324A - Safety device for gas heating appliances - Google Patents

Abstract

A naked-flame safety device for gas heating appliances has a pipe pilot burner (3) for the pilot flame, comprising at least one flange (20) forming an extension of the free end of the pipe (18). A thermocouple element (21) is fixed to the flange (20) so as to form a thermoelectric couple with the pipe (18). A spark igniter (4) is associated with the pilot burner. <IMAGE>

Description

SPECIFICATION Safety device for gas heating appliances The present invention relates to a naked-flame safety device of the type comprising a bracket to which are fixed a pipe pilot burnerforthe pilot flame, an insulating spark plug forming part of a spark igniter forthepilotflameinsidethesaid burneranda thermocouple element fixed to the pipe of the burner and forming athermoelectriccouplewiththesaid pipe.

A safety device of this type is described in detail in PatentApplication No.22721 A/82 f;led on 3August 1982 in the name of the same Applicant.

These safety devices are widely used in gas heating applicances such as catalytic infra-red ray heaters, boilers, water heaters and the like, intended to be installed in closed rooms.

Theirfunction isto interrupt operation ofthe heating appliance when the percentage of oxygen present in the atmosphere ofthe room in which the appliance is installed falls below a given threshold value.

The appliance described in the abovementioned patent application is efficient and reliable in this respect. However, in practice, it is difficult and complex to manufacture.

The aim ofthe present invention is to provide a naked-flame safety device which is suitable for installation in gas heating appliances and which is simple and economical to construct and assemble.

This aim is achieved by means of a device ofthe abovementioned type, characterized in that it comprises at least one flange forming an extension cfthefree end ofthe pipe, the said thermocouple element being fixed to the said flange.

The characteristicfeatu res and advantages ofthe invention will emerge more clearly from the detailed description which follows, of a preferred but not exclusive embodiment thereof, illustrated, by way of a non-limiting example, with reference to the attached drawings in which: Figure lisa perspective view of a naked-flame sa fety device according to the present invention; Figure2 is a cross-sectional view ofthe safety device shown in Figure 1.

With reference to the Figures mentioned, a naked-flame safety device, denoted in its entirety by 1, is provided with a support bracket 2 fixed inside a gas heating appliance which is per se conventional and not shown.

The bracket 2 comprises a flat portion 2awhich extends horizontally and along one corresponding side of which respective lugs 2b provided with holes protrude vertically, at opposite ends.

A pilot burner3 and a spark igniter4are fixed to the bracket 2.

The pilot burner3 has a tubular body 5 with an axis X-X extending vertically relative to the flat portion 2a. The body 5 has a first end and a second end which are located axially opposite each other and are indicated by 6 and 7, respectively.

At the bottom end 6 there is formed, inside the body 5, a threaded seat 8 for receiving a bush-type connection piece 9 for connecting the burner3 to a gas supplytube (not shown).

The connection piece 9 is tubular and coaxial with the body 5. Inside it there is mounted a capsular nozzle 10 with a hole in the centre and a fine-mesh filter 11.

The body 5 consists of two coaxial sections, a lower section 12 extending from the end 6 and having a polygonal (hexagonal) external profile, and an upper cylindrical section 13 leading to the end 7.

The section 12 has two radial through-holes 15 which have a diameter K and supply primary airto the burner 3.

The holes 15 lead into a mixing cnar,1ber 16. A mixing tube 17 extends from the chamber 16 asfaras the upper end 7 of the body 5. This mixing tube has an internal diameter H. The ratio H1K between the internal diameterofthe mixing tube 17 and the diameter ofthe holes 15 has a value which is preferably between 1 and 2.

At the free end 7 ofthe upper section 13 ofthe body Sthere is mounted a pipe 18 with a tubular cylindrical portion 19 which has an internal diameterA and from the free end of which twojuxtaposed flanges 20 extend axially.

Theflanges20arearrangedata distancefrom each other and are joined to the perimeter ofthefree end ofthe portion 19 over an area constituting between 0.2 and 0.7 ofthe perimeter (circumference) ofthe abovementioned portion 19.

The axial extension ofthe flanges 20, from thefree end ofthetubular portion 19, is preferably between 2 and 8 mm. The ratio between the internal diameterA of the pipe 18 and the axial extension of the flanges 20 is preferably between 0.8 and 1.7. Moreover, the ratio between the axial extension of the flanges 20 and the distance between the free end ofthe pipe 18 and the nozzle 10 is preferably between 6 and 8.

Again by way of preference, the ratio between the internal diameter A of the pipe 18 and the diameter K ofthe holes 15 has a value of between 1.8 and 2.7, and the ratio between the diameter of the holes 15 and the diameter of the hole provided in the nozzle 10 has a value of between 8 and 16.

To one of the flanges 20 there is fixed, by means of electricspotwelding, athermocoupleelement2l made of material suitableforforming a hot thermocouple junction with the pipe 18.

An electrical cable 22 is connected to the element 21, this cable being protected by an insulation 23 and being conventionally connected to a solenoid valve (notshown) for interrupting the gas supply to the heating applicance with which the safety device 1 is associated.

The spark igniter4comprises a spark plug 24 which is made of electrically insulating material and has an axis Y-Y extending parallel to the axis X-X,the two axes being located at a distance from each other, and also a rod-shaped element 26 which is electrically conductive and which extends coaxially and integrallythroughthe spark plug 24.

The rod-shaped element26 has a free end 27 which is bent at 90 degrees and is located above the end ofthe pipe 18. It is connected to an electrical generator (not shown) and forms, in a mannerwhich is per se conventional, the electrode for igniting a pilotflame inside the burner 3.

The body 5 ofthe burner3 and the spark plug 24of the igniter 4 engage inside respective seats 30 and 31 formed in the portion 2a of the bracket 2. An interlocking connection is obtained by positioning the lower section 12 ofthe body 5 inside the seat 30 and the spark plug 24 inside the seat 31 and then producing deformations locally by upsetting the edges of the seats 30 and 31, as indicated by 32 and 33, respectively, in Figure 1.

The safety device 1 operates as follows. By supplying a suitable combustible gas to the burner3, a pilot flame is madeto burn in the region ofthe pipe 18.

The amount of primary air mixed with the combustible gas supplying the pilot flame is limited by the diameter and the position of the holes 15.

When there is a normal amount of oxygen in the atmosphere, the pilotfiame burns between the flanges 20, heating the latter and in particularthe hot thermocouple junction formed between the pipe 18 and the thermocouple element 21.

An electromotive force is thus generated, which causes opening of a solenoid valve supplying combustible gas to a gas heating appliance associated with the safety device 1.

When the amount of oxygen in the atmosphere falls below a threshold value, for example owing to insufficient air circulation in the room where the heating appliance is installed, the pilot flame is gradually moved upwards until combustion occurs above the flanges 20.

The flange 20 forming the hot thermocouple junction with the element 21 cools as the electromotive force generated decreases. This causesthe solenoid valve, by means of which the supply to the gas heating appliance is controlled,to close and hence the abovementioned appliance to be switched off.

Substantially similar results have been obtained by replacing the pipe 18with a pipe having only one flange 20, to which the element 21 is welded and which is joined to the perimeter of the free end ofthe tubular cylindrical portion 19 overan area constituting between 0.1 and 0.6 of the perimeter of the pipe, with a pipe having three flanges joined to the perimeterofthe portion l9overanarea constituting between 0.2 and 0.7 ofthe circumference ofthe abovementioned portion 19.

It will of course be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope ofthe invention.

Claims (7)

CLAiMS

1. Naked-flame safety device comprising a bracketto which are fixed a pipe pilot burnerforthe pilot flame, an insulating spark plug forming part of a spark igniterforthe pilot flame inside the said burner, and a thermocouple elementfixed to the pipe of the burner and forming a thermoelectric couple with the said pipe, characterised in thatthe pipe pilot burner comprises at least one flange forming an extension ofthefree end ofthe pipe, the said thermocouple element being fixed to the said flange.

2. Device according to claim 1 characterised in that it comprises at least two flanges arranged ata distance from each other and inthatthe said flanges are joined to the perimeter ofthe said pipe over an area constituting between 0.2 and 0.7 ofthe perimeter of the pipe itself.

3. Device according to claim 1 characterised in that the said flanges extend axially by about2-8mm from the free end of the pipe.

4. Device according to claim 1 characterised in that the ratio between the value of the internal diameter ofthe pipe and the value of the axial extension ofthe flanges is between 0.8 and 1.7.

5. Device according to claim 1 characterised in that the said burner is received inside a seating formed in the said bracket,the said seat being deformed locally along its own edge so as to achieve an interlocking connection between the said burner and the said bracket.

6. Device according to claim 1 characterised in that the said insulating spark plug ofthe spark igniter is received inside a seat formed in the said bracket, the said seat being deformed locally along its own edge so as to achieve an interlocking connection between the said spark plug and the said bracket.

7. A device substantially as hereinbefore described with reference to the accompanying drawings.