EP0744582A1 - Safety device preventing the return of combustion gases in bath heaters or gas-fired boilers - Google Patents

Abstract

The device comprises a heat sensitive element (10). This sensor detects the flow back of combustion products from the outlet flow in the apparatus draw chimney (3). The heat sensor is positioned outside the chimney behind the apparatus at the level of an opening (8) in the rear face (9). Fresh air normally is induced in this region. The opening is in the extension of a central diverter (7) located inside the chimney casing directly below the exhaust gas duct (4). The central diverter has the shape of a longitudinal small dish whose concavity is upwards.

Description

The invention relates to a safety device reacting to the discharge of combustion products in bath heaters and gas boilers and relates more specifically to a particular positioning of the temperature sensor in the device.

It is well known to use safety devices which react, for example when the thermal draft in the device is accidentally or momentarily insufficient, to stop it. For this it is usual to place a heat-sensitive element, for example a bulb or a switch, at a location in the draft hood where it will be likely to be reached by a flow of repressed fumes. When the operation is normal the sensor is in a flow of fresh air and does not act. On the other hand, in the event of abnormal operation when the exhaust duct is blocked, it is subjected to a flow of combustion products at a higher temperature.

For the system to operate without inadvertent tripping, the temperature differential between low-power operation under abnormal discharge conditions and normal high-power operation must be as wide as possible to compensate for the variation in ambient temperature in summer. .

However, until now, the thermosensitive element has been placed on the right dawn or the left dawn of the draft hood, and therefore subjected to thermal radiation from the housing of this draft hood which brought it to temperatures close to those combustion products during backflow at low power. In summer, with ambient temperatures of around 30 ° C, these systems inadvertently become safe.

To overcome this drawback, the Applicant has developed a particular device, always using a temperature sensor capable of detecting untimely overheating, but placed in a very particular position taking advantage of the natural draft of fresh air in the device. .

A main object of the present invention therefore consists of a safety device against the backflow of combustion products in bath heaters and gas boilers comprising a heat-sensitive element placed in the flow of delivery of combustion products in the draft hood of the device during insufficient draft or blockage of the smoke evacuation duct, device according to which the heat-sensitive element is positioned outside the draft hood, behind the device and at the level of a hole provided on the back side.

According to a particular characteristic of the invention, the orifice is in the extension of a central blade disposed inside the draft-cutting box directly above the smoke evacuation duct.

Advantageously, the central blade has the shape of a longitudinal cup whose concavity is turned upwards.

The particular characteristics and advantages of the invention will be seen on reading the following description of an exemplary embodiment in which reference is made to the appended drawings which represent:

Figures 1 and 2 schematic views in vertical section, respectively from the side and from the front, of the device in normal operation.

Figure 3 a partial perspective view of the central part of the draft hood.

Figures 4 and 5 schematic views identical to Figures 1 and 2, showing the device in the event of abnormal operation.

Partly shown in Figures 1 and 2, a boiler equipped with a burner 1, a hot skirted heating body 2 surmounted by a draft-reducing unit 3 and a flue exhaust duct 4. The draft hood has in known manner lateral air inlets 5 and deflectors 6 above these air inlets. There is also in the housing, a central blade 7 directly above the conduit 4, which extends over the entire depth of the apparatus, up to an orifice 8 located in the extension, provided on the rear face 9 of the draft hood as illustrated in FIG. 3. The central blade 7 has the shape of a longitudinal cup whose concavity is turned upwards.

The thermosensitive element 10 or sensor is mounted behind the boiler and outside the draft hood, at the orifice 8.

Figures 1 and 2 show the boiler in normal operation. In this case, the combustion products follow a path materialized by the arrows 11, between the heating body 2 and the exhaust duct 4, while a natural draft of fresh air is established in particular behind the appliance and enters inside by the orifice 8 as shown by the arrows 12. Thus positioned, the thermo-element is outside the thermal radiation emitted by the draft-reducing unit 3. It is also found in a large flow of fresh air thanks to which it is kept at a temperature very close to room temperature. The natural draft behind the appliance is particularly due to the fact that the top of the boiler is hotter than the bottom. In addition, the fact that the heat-sensitive element 10 is located at the level of the central vane 7 enables it to be in an overpressure zone relative to the housing of the draft hood in normal operation. Indeed in natural draft, the central vane is an obstacle to the flow of fumes which bypass it then are sucked through the duct 4. The relative acceleration of these fumes above the dawn creates a depression in the center of it. ci, in its hollow part, which means that the internal zone of the draft hood close to the orifice 8 is in depression relative to the outside of the rear face 9, that is to say relative to in the zone where the thermosensitive element is located 10. There is therefore no risk that the combustion products escape through the orifice and go to heat said sensor.

In the case illustrated in FIGS. 4 and 5, of a discharge, an insufficient draft or a blockage of the conduit 4, the housing 3 of the draft hood is in overpressure relative to the heat-sensitive element 10. A flow of hot smoke will therefore escape through orifice 8 as shown by the arrows 11. The device is then made safe by opening the contact of the sensor as soon as the temperature of the latter has exceeded a predetermined threshold.

Thanks to this particular position of the heat-sensitive element, the safety margin in relation to variations in ambient temperature is notably increased, which makes it possible to avoid untimely tripping of the device.

The thermosensitive element thus placed behind the draft hood, can quickly put the boiler in safety, whatever the power adjusted between a minimum power and a maximum power. This avoids the use of two sensors or a single sensor but at two cut-off levels.

Claims (3)

Safety device against the backflow of combustion products in gas-fired bath heaters and boilers, comprising a thermosensitive element placed in the flow of combustion products backflow when the appliance is draft proofed during insufficient draft or a plugging of the smoke evacuation duct, characterized in that the heat-sensitive element (10) is positioned outside the draft-cutting box (3), behind the appliance and at the level of an orifice (8) provided on the rear face (9). Safety device according to claim 1, characterized in that the orifice (8) is located in the extension of a central blade (7) disposed inside the draft-cutting box (3) directly above the duct. (4) smoke evacuation. Safety device according to claim 2, characterized in that the central vane (7) has the shape of a longitudinal cup whose concavity is turned upwards.

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