EP0744582B1 - 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 boilers and bath heaters gas comprising a reactive safety device the discharge of combustion products, and carries more precisely on a particular positioning of the temperature in the device.

It is well known to use security, for example GB-A- 2 143 943, which react, for example when the draw thermal in the device is accidentally or momentarily insufficient to stop it. For that it is usual to place a thermosensitive element, for example a bulb or a switch, at a place in the draft stop where it will likely be reached by a flow of repressed fumes. When operation is normal the sensor is in a flow of fresh air and does not act. Through against in the event of abnormal operation when the discharge pipe, it is subjected to a flow of higher temperature combustion products.

So that the system works without disjunction untimely, the temperature differential must be between low power operation in abnormal discharge conditions and operation normal at high power, as wide as possible for compensate for the variation in ambient temperature in summer.

However until now the thermosensitive element was placed on the right dawn or the left dawn of the draft hood, and thereby subjected to thermal radiation from the housing of this draft hood which brought it to temperatures close to those of the products of combustion during a backflow at small power. In summer, with ambient temperatures of around 30 ° C, these systems turn on unexpectedly security.

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

A main object of the present invention therefore consists of a gas boiler or bath heater including a back-up safety device combustion products with one element thermosensitive placed in the delivery flow of combustion products at the draft hood of the appliance when insufficient draft or blockage of the duct smoke evacuation, the heat-sensitive element being positioned outside the draft hood, behind the device and at a hole provided on the face rear, device according to which the orifice is in the extension of a central blade arranged inside the draft-reducing box directly above the exhaust duct fumes.

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

The special features and advantages of the invention will be seen on reading the description following of an exemplary embodiment in which we refers to the accompanying drawings which represent:

Figures 1 and 2 schematic sectional views vertical, respectively side and 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 are identical schematic views Figures 1 and 2, showing the device in case of abnormal operation.

Partially shown in FIGS. 1 and 2, a boiler equipped with a burner 1, a heating body with hot skirt 2 surmounted by a draft hood 3 and a smoke evacuation duct 4. The draft hood in known manner has side air inlets 5 and deflectors 6 above these air inlets. There is also in the case, a central blade 7 directly above the conduit 4, which extends over the entire depth of the device, up to an orifice 8 located in the extension, provided on the rear face 9 of the draft hood as illustrated in Figure 3. The central blade 7 has the shape of a longitudinal cup whose concavity is turned towards the high.

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

Figures 1 and 2 show the boiler in normal running. In this case the products of combustion follow a path materialized by arrows 11, between the heating body 2 and the duct 4, while a natural draft of fresh air is established in particular behind the device and penetrates inside through hole 8 as shown by the arrows 12. Thus positioned, the thermo-element is outside the thermal radiation emitted by the draft hood 3. It is also in a large flow of fresh air thanks to at which it is kept at a temperature very close to the ambient temperature. The natural print behind the device is particularly due to the fact that the top of the boiler is warmer than the bottom. Furthermore the fact that the element thermosensitive 10 is at the level of the central vane 7 allows it to be in an overpressure zone compared the housing of the draft hood in normal operation. In effect in natural draft, the central dawn is an obstacle to flow of fumes which bypass it then are sucked in by the conduit 4. The relative acceleration of this smoke above of dawn creates a depression in the center of it, in its hollow part, so that the internal area of the housing draft hood near orifice 8 is under vacuum relative to the outside of the rear face 9, that is to say relative to the area where the thermosensitive element is located 10. There is therefore no risk that the products of combustion escape through the orifice and go to heat said sensor.

In the case illustrated in Figures 4 and 5, a backflow, insufficient draft or blockage of the conduit 4, the housing 3 of the draft cutter is located overpressure with respect to the heat-sensitive element 10. A flow of hot smoke will therefore escape through orifice 8 as shown by the arrows 11. Securing the the device is then made by opening the contact of the sensor as soon as its temperature has exceeded one predetermined threshold.

Thanks to this particular position of the element thermosensitive, the safety margin compared to room temperature variations is markedly increased which avoids untimely disjunction of the device.

The heat-sensitive element thus placed behind the draft hood, can quickly turn the boiler on safety, whatever the power adjusted between a minimum power and maximum power. It avoids the use of two sensors or one sensor but two cutoff levels.

Claims (2)

1. Gas-fired boiler or bath heater comprising a safety device against the return of the combustion products, comprising a heat-sensitive element (10) placed in the return flow of the combustion products at the damper of the appliance in the event of an insufficient draught or of a blockage of the smoke discharge pipe, the heat-sensitive element (10) being positioned outside the damper housing (3), behind the appliance and level with an orifice (8) provided on the rear face (9), characterized in that the orifice (8) is located in the extension of a central vane (7) arranged inside the damper housing (3) in vertical alignment with the smoke discharge pipe (4).
2. Gas-fired boiler or bath heater according to Claim 1, characterized in that the central vane (7) is in the form of a longitudinal dish, the concavity of which faces upwards.

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