FR2734626A1 - SAFETY DEVICE AGAINST THE DISCHARGE OF COMBUSTION PRODUCTS INTO BATHROOMS AND GAS BOILERS - Google Patents

Abstract

The thermosensitive element (10) reacting to the discharge of combustion products at the draft hood of the appliance, when there is insufficient draft or if the smoke outlet duct (4) is blocked, is positioned outside the draft hood (3), behind the device, and at an opening (8) provided on the rear face. Application to gas bath heaters and boilers.

Description

The invention relates to a safety device responsive to the

  delivery of the products of combustion in the bath heaters and gas boilers and relates more specifically to a particular positioning of the temperature sensor in the apparatus. It is well known to use safety devices which react, for example when the thermal draft in the apparatus is accidentally or temporarily insufficient, to put it to a standstill. For this it is usual to place a thermosensitive element, for example a bulb or a switch, at a location of 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 fresh air flow and does not act. On the other hand, in the event of abnormal operation during the plugging of the evacuation pipe, it is subjected to a flow of

  combustion products at higher temperature.

  For the system to operate without untimely tripping, the temperature differential between low power operation under abnormal discharge conditions and normal high power operation must be as wide as possible for

  to compensate for the variation of ambient temperature in summer.

  So far the heat-sensitive element was placed on the right vane or the left vane of the draft hood, and thus subjected to thermal radiation from the housing of this draft hood which brought it to temperatures close to those combustion products during a small power delivery. In summer, with ambient temperatures in the order of 30 C, these systems are inadvertently 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 is therefore a safety device against

  repression of combustion products in the heaters

  baths and gas boilers comprising a thermosensitive element placed in the discharge flow of the products of combustion at the draft hood of the apparatus during an insufficient draft or a clogging of the flue gas duct, a device according to which the 'element

  thermosensitive is positioned outside the housing

  draw, behind the device and at a planned orifice

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 hood housing.

  in line with the flue pipe.

  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 perceived on reading the description

  following of an embodiment in which reference is made to the accompanying drawings which represent: FIGS. 1 and 2 diagrammatic views in vertical section, respectively from the side and from the front, of the apparatus

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 case of

abnormal operation.

  FIGS. 1 and 2 show partially a boiler equipped with a burner 1, a hot skirted heating body 2 surmounted by a draft hood 3 and a flue gas discharge duct 4. The draft hood housing has known manner of side air inlets 5 and baffles 6 above these air inlets. There is also in the housing, a central blade 7 in line with the conduit 4, which extends over the entire depth of the device, to an orifice 8 located in the extension, provided on the rear face 9 of the casing as shown in Figure 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 housing

draw, at the orifice 8.

  We see in Figures 1 and 2 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 pipe 4, while a natural draft of fresh air is established in particular behind the apparatus and penetrates internally through the orifice 8 as shown by the arrows 12. Thus positioned, the thermoelement is outside the thermal radiation emitted by the draft hood 3. It is also in a large flow of fresh air thanks to which it is kept at a temperature very close to the ambient temperature. The natural draft behind the unit is due especially to the fact that the top of the boiler is hotter than the bottom. In addition, the fact that the thermosensitive element 10 is at the level of the central blade 7 allows it to be in a zone of overpressure with respect to the casing of the draft hood in normal operation. Indeed in natural draft, the central dawn is an obstacle to the flow of fumes that surround it and are sucked through the pipe 4. The relative acceleration of these fumes above the dawn creates a depression in the center of it. ci, in its hollow part, so that the inner zone of the draft hood housing near the orifice 8 is in depression relative to the outside of the rear face 9, that is to say relative to in the zone o is the thermosensitive element 10. There is therefore no risk that the products of combustion escape through the orifice and go warm

said sensor.

  In the case illustrated in FIGS. 4 and 5, of a discharge, an insufficient draft or a plugging of the duct 4, the casing 3 of the draft hood is in overpressure with respect to the thermosensitive element 10. hot flue gas flow will therefore escape through the orifice 8 as shown by the arrows 11. The security of the device is then by opening the sensor contact as soon as the temperature thereof has exceeded a

predetermined threshold.

  Thanks to this particular position of the thermosensitive element, the margin of safety with respect to the variations of ambient temperature is notably increased, which makes it possible to avoid untimely disjunctions of the apparatus. The thermosensitive element thus placed behind the draft hood, can quickly put the boiler safe, whatever the adjusted power between a minimum power and a maximum power. This avoids the use of two sensors or a single sensor but two

cutoff levels.

Claims (3)

  1.- Safety device against the discharge of the products of combustion in the bath heaters and gas boilers comprising a thermosensitive element placed in the discharge flow of the products of combustion to the draft hood of the apparatus during an insufficient drawing or a plugging of the flue gas duct, characterized in that the heat-sensitive element (10) is positioned outside the draft hood (3), behind the appliance and at an orifice (8). ) provided on the face rear (9).   2.- Safety device according to claim 1, characterized in that the orifice (8) is in the extension of a central blade (7) disposed inside the draft housing (3) to the plumb line (4) smoke evacuation.   3. Safety device according to claim 2, characterized in that the central blade (7) has the shape of a longitudinal cup whose concavity is tounée to the top.