EP1060347B1 - Integrated security system for smoke extractor - Google Patents

Description

The present invention relates to a security system incorporated in an extractor smoke that is placed at the outlet of the chimney flue of any room, by example of a dwelling, individual or collective, this extractor being equipped with a mechanical suction device, such as a turbine driven in rotation by a motor, especially electrical, so as to generate a vacuum in the duct which sucks the burnt gases and / or stale air in the space of the room to which the duct is connected.

Extractors of this type, to which the present applies in particular invention, are described in particular in documents FR-A-2 459 424, FR-A-2 709 534 and FR-A-2 711 770, which relate to mixed devices, capable of ensuring the ventilation of the room both static (engine stopped), under the action of the wind (by effect Venturi), only in dynamic, by mechanical aspiration in the duct. In the solutions described in the aforementioned patent documents, the suction of gases in the duct, from bottom up is obtained - surprisingly enough - by blowing a flow of air, through the turbine, from top to bottom, towards the mouth of the duct, a contoured base surrounding the latter ensuring the deflection of air outwards and down to get this result.

A malfunction of the mechanical suction device, in particular due to a failure of the electric motor which ensures its training, can have effects harmful to the health of people in the home.

This is the case, in particular, when the dwelling is equipped with a boiler whose burnt gases, harmful, are likely - failing to be properly evacuated - to accumulate in inhabited rooms.

It is quite common, moreover, that the same house has two separate exhaust ducts, each equipped with a type extractor mentionned. One of the conduits - called sanitary - connects to the W.C. and the rooms baths ; the other - called main - is connected to the other rooms, including the kitchen. In case of failure of the extractor fitted to the main duct; the sanitary extractor ensures evacuation, more or less efficient, air present in all rooms; this assumes a passage of stale air inside the house, to the sanitary rooms in which takes place the evacuation. This transit can also cause health problems, especially if the stale air is harmful, as it is if it comes directly from a boiler.

We have already tried to overcome these difficulties by mounting on the electrical circuit engine control that drives the extractor turbine a non-power detector. Thus, in the event of an interruption in the supply (in particular failure of current), the detection thus produced triggers an event safe, for example shutting down the boiler.

This solution is not always suitable.

Indeed, it may happen that the turbine rotation stops at caused by a foreign body, such as a bird, which has entered and been found blocked inside the extractor, immobilizing the turbine blades. In this hypothesis, the electric motor - although blocked - is still powered and, therefore, the detection mentioned above does not take place.

It has also been proposed to install a sensor inside the duct. pressure. If the suction stops - or if the suction is insufficient - the vacuum normally measured in the duct stops; the pressure there is equal (or approximates) atmospheric pressure. This abnormal measurement triggers the security event.

This solution can be envisaged if the depressions occur developing in the conduits are relatively strong, on the order of a hundred Pascal, or more. Indeed, one can in this case make use of pressure switches. It is robust, reliable and inexpensive pressure sensors which act as switches. A pressure switch has two opposite pressure chambers connected by nozzles, one at low pressure (vacuum) and the other at high pressure (pressure atmospheric); they are separated by a membrane whose deformation in one direction ensures electrical contact while, in the other direction, it cuts the circuit. If the vacuum in the duct is sufficient, the state of the pressure switch can therefore allow the electrical supply to the boiler. Otherwise, which is a sign of extractor malfunction, it interrupts it

Unfortunately, this solution is not satisfactory when working in conditions of relatively low depression, of the order of 5 to 10 Pascal, as this is often the case with mixed extraction systems (static / dynamic). Indeed, under such conditions, the sensitivity of the pressure switch has a value whose magnitude is same order or even higher than that of the depression in the duct. The phenomena of siphoning, which can simply result from the opening of a window in the house, can then disturb the flow of air - and correspondingly its pressure - in the led, causing untimely triggering of the security event.

Another drawback, linked to the location of the air intake in the duct of smoke, is that of rapid fouling of the pressure switch.

This problem is also encountered in the device described in the FR-A-2 550 317 which uses a pressure switch capable of comparing the value of the vacuum at the level of a pressure-reducing organ, such as a Venturi neck, either with pressure atmospheric, either with a reference pressure constituted by the pressure of discharge of the boiler burner fan, in order to control if necessary stopping the operation of said burner, via a contactor.

Indeed, in this known solution the air intakes of the pressure switch are positioned just at the outlet of the boiler, in the flue gas flow, and are located by therefore directly exposed to fouling.

In addition, the permanent fluctuation of depressions, linked in particular to wind disturbances cause practical difficulties in operating the boiler, because the flow generated by the burner fan and, correspondingly, the value of the overpressure and vacuum are relatively low in the outlet duct of boiler; we therefore observe frequent and untimely stops and restarting of the boiler due to these fluctuations.

The security device described in document FR-A-2 631 687 includes a mechanical exhaust fan capable of stopping the operation of boilers when the fan stops.

For this purpose, the fan is equipped with a pressure switch capable of detecting the fan malfunction in order to open a shutter located in the lower part of the extraction duct and cause the boiler to shut down.

No information is given in this document as to the mode of operating the pressure switch or at the location of its air intakes.

The present invention aims to solve the problems mentioned above, by proposing to safely control the proper functioning of the device mechanical suction, while making use of a usual differential pressure sensor whose reliability is proven and recognized, whose air intakes are positioned at the interior of a clean, or practically clean, air stream, the cost of which is relatively weak, namely a pressure switch.

This objective is achieved, in accordance with the invention, thanks to the fact that the security system has two separate air intakes incorporated into the extractor and arranged in locations where, the suction device being in operation, the pressure is respectively lower and higher than atmospheric pressure ambient, these air intakes being respectively connected respectively to the nozzles of depression and pressure of a pressure switch forming a switch, the latter being adapted to trigger a safety event when the difference between the relative values of the overpressure and depression detected by the air intakes drops below a threshold value determined.

So the difference (subtraction) between the two relative numbers that are the values of the overpressure (positive) and that of the depression (negative), amounts to add their absolute values, so that the pressure switch is under pressure sufficient differential with respect to its sensitivity threshold. The captured air is clean.

Advantageously, the air intake which is connected to the nozzle of pressure switch pressure is placed inside a vacuum chamber whose air inlet section is reduced by a throttle and / or a filter, so as to create a pressure drop at this level, and thus increase the value of the vacuum in said bedroom.

In a preferred embodiment, applicable to an extractor having a suction device consisting of a centrifugal turbine, mounted rotating inside a cuff, against which the air generated by the turbine, the air intake connected to the pressure end of the pressure switch is placed on the inner wall of this cuff.

In a variant, in which the suction device is a turbine double, comprising a set of upper blades and a set of lower blades, the socket of air which is connected to the pressure end of the pressure switch is placed above the set of upper blades.

Advantageously, when the turbine is mounted at the base of a shaft vertical outlet of an electric motor housed inside a vacuum chamber in which the air flow circulates from the top to the bottom, the air intake which is connected to the pressure switch vacuum nozzle is placed in this chamber.

In one possible application, the security system is associated with a duct which evacuates burnt gases coming from at least one boiler, the pressure switch being suitable for controlling the shutdown of the boiler.

In another possible application, it is associated with the sanitary conduit a dwelling in which other rooms have at least one other duct with a similar extractor having a mechanical extraction device actuated by a motor, the pressure switch being adapted to control the stopping of this motor.

Other characteristics and advantages of the invention will become apparent from the description which will now be made of it, with reference to the appended drawings, which illustrate a possible embodiment.

• la figure 1 est une vue de face schématique, coupée par un plan de symétrie vertical, d'un extracteur de type usuel pourvu d'un système de sécurité conforme à l'invention ;
• la figure 2 est une vue de dessus de l'extracteur de la figure 1, coupée par le plan horizontal référencé II-II sur cette dernière ;
• la figure 3 est un schéma des circuits pneumatique et électrique du système.

In these drawings:

• Figure 1 is a schematic front view, cut by a vertical plane of symmetry, of a conventional type extractor provided with a security system according to the invention;
• Figure 2 is a top view of the extractor of Figure 1, cut by the horizontal plane referenced II-II on the latter;
• Figure 3 is a diagram of the pneumatic and electrical circuits of the system.

The extractor represented in FIGS. 1 and 2 is of the same general type as that described in FR-A-2 711 770 already mentioned.

This extractor 2 is installed at the upper open end of a chimney flue 1.

It has a symmetry of revolution around the vertical axis ZZ ' of the duct.

The upper part of the duct 1 is surrounded by a base 20.

The device comprises an electric motor 3, of axis ZZ ' , protected by a dome 21.

The motor output shaft 3, referenced 30, carries an effect turbine 6 centrifugal.

In the illustrated embodiment, the turbine is a "double turbine". It includes a horizontal disc 60 which carries, on its upper face, a set of blades 61, of relatively low height, and on its underside, another set of blades 62, of greater height.

This arrangement is illustrated in FIG. 4 of the aforementioned patent, to which can refer to if necessary.

The motor 3 is housed inside a cup 5, of profiled shape, open upwards under the dome 21and downwards, towards the central zone of the disc 60.

The upper entry section of the cup 5 is reduced by a rim 51; in addition, the opening of the cup is fitted at this level with a filter 500. The presence of the narrowing 51 and of the filter 500 creates a pressure drop which has the effect of increasing the vacuum inside the cup, when the extractor is in service.

The cup 5 has a discoid base 52 open in its part central, to allow the passage of the air flow downwards.

The centrifugal turbine 6 is surrounded by a ferrule, or sleeve 4 approximately cylindrical, open both upwards and downwards.

A set of suitable flanges and spacers, not shown on Figure 1, are naturally provided to ensure the mutual fixing of these different elements, in the position shown.

This extractor is of the mixed type, which means that it can be used both static, engine 3 stopped, and dynamic, engine 3 running.

Static operation is possible when there are wind conditions satisfactory exterior; the passage of the wind in the free space separating the base 20 from the cuff 8 has the effect, by a Venturi phenomenon, of causing a suction of stale air, from top to bottom in the duct 1, which ensures the desired evacuation.

When the wind conditions are not satisfactory - or for others reasons -, motor 3 is started.

An air circulation is then observed which is symbolized in FIG. 1 by the arrows i .

The rotation of the turbine 6 is symbolized by the arrow R. The upper blades 61 generate a suction of air from the top to the bottom inside the cup 5.

The air enters the extractor through the opening of the dome 21, goes upwards, then descends through the filter 500 into the interior space 50 of the cup, space which will be designated "vacuum chamber".

It will be noted that the passage of air around the motor 3 participates in its cooling during operation.

Air flows from top to bottom of the vacuum chamber 50 through the central opening of the cup base 52.

In the lower part of the cup 5, the moving blades 61 and 62 generate a relatively large air flow towards the outside, by centrifugal effect, against the wall internal of the cuff 4. This air flow is deflected downwards by said wall and goes come to lick the profiled surface, for example frustoconical with rounded edges, and divergent down from the base 20.

This results in a phenomenon of aspiration in the duct 1.

During this process, a distribution is established in the extractor relatively stable air pressure.

If we take ambient atmospheric pressure as a reference, we observes inside the chamber 50, and in particular at its base, a depression (strong pressure) relatively strong. This is linked to the pressure drop at the inlet of the chamber, which induces a phenomenon of significant suction; on the contrary, we observe at proximity of the wall of the sleeve 4, and in particular facing the blades 62, a fairly high overpressure (positive pressure).

According to the invention, are installed in these two places air intakes referenced respectively 7 and 8.

As illustrated in FIG. 3, the air intake 7, which senses a negative pressure p-, is connected, via a suitable pneumatic conduit, to the vacuum nozzle 90 of a pressure switch 9.

Similarly, the air intake 8, which senses a positive pressure p + , is connected to the pressure end piece 91 of this pressure switch.

In known manner, the pressure switch 9 comprises a membrane 900 which is exposed to the opposing pressures of the fluid supplied to each of its end pieces 90, 91. This membrane controls a switch I which is closed when the differential pressure on the two sides of the membrane is greater at a predetermined threshold value, generally adjustable. This switch is mounted on an electrical circuit supplied by a generator G - which can be the mains supply - and carrying an actuator A of electrically controlled safety event. In one possible embodiment, this actuator is, for example, a relay controlling the solenoid valve for stopping the boiler located in the room equipped with conduit 1.

When the differential pressure sensed by the two air intakes 7 and 8 is sufficient, the switch I is closed, and the relay A is in a state which authorizes the operation of the boiler. On the other hand, if the differential pressure falls below the threshold value, in particular if it becomes zero, the switch I opens, and the relay A switches to a state which causes the boiler to stop.

As an indication, the relative values of pressures p + and p- are respectively +60 and - 60 Pascal.

The difference between these two pressures is therefore 60- (- 60) = 120 Pa.

A differential pressure of 120 Pa is therefore obtained, which is clearly greater than the usual sensitivity of a pressure switch, which is normally understood between 10 and 50 Pascal, depending on the model. The risks of inadvertent triggering of the security system are thus limited.

The pressure switch 9 is set for example so that the switch I opens when this differential pressure is less than 50 Pascal.

The operation of the system is very simple. In the event of the turbine 6 stopping for any reason whatsoever (failure of the engine 3, or blockage of the blades in particular), the air pressure at the air intake 7 is close to the air pressure at level of the air intake 8, so that the differential pressure is insufficient in the pressure switch 9 to keep the switch I closed.

This consequently causes the relay A toggle and the boiler to stop.

The production of burnt gases in the room whose ventilation is not properly insured therefore ceases.

It should be noted that the centrifugal turbine 6 does not necessarily have to be completely stopped so that the security system is triggered.

Indeed, if the speed of rotation of the turbine is abnormally low, for example as a result of undesirable friction of a deformed blade against the sleeve 4, the differential pressure supplied to the pressure switch 9 may be insufficient to keep the switch I closed ; of course, the adjustment of the threshold value of the pressure switch will be carried out according to the operating conditions of the extractor concerned, to avoid inadvertent tripping.

The nature and function of actuator A can be varied, depending on the safety event to be triggered.

It could just be an alarm for example.

As already mentioned above, it can also be the command stop of another extractor, this one equipping another conduit connected to the same dwelling than the extractor concerned by the invention.

The location of the air intakes 7 and 8 will preferably be chosen from the optimally, depending on the model and configuration of the extractor concerned, the socket 8 being advantageously placed where the overpressure is strongest and the socket 7 being ideally placed where the depression is maximum.

In a variant of the device, the air intake 8 could be placed under the horizontal base 52 of the cup 5, above the upper blades 61 of the double turbine. The overpressure is high in this area.

Note that the air intakes are installed, not in the duct chimney, but inside the extractor, in spaces crossed by clean air - or practically clean - the risk of fouling the pressure switch by smoke is eliminated or, at the very least, significantly reduced.

The invention obviously applies to extractors having mechanical suction means different from the centrifugal turbine with which the embodiment described above. It applies in particular to propeller extractors or a cage-shaped turbine.

Claims (7)

1. A safety system incorporated in a smoke extractor (2) placed at the outlet of a duct (1) and fitted with a mechanical suction device (6) such as a turbine suitable for generating suction in the duct (1), the system being characterized by the fact that it has two separate air tapping points (7, 8) incorporated in the extractor (2) and disposed at locations where air pressure, when the suction device (6) is in operation, is respectively less than and greater than ambient atmosphere pressure, these air tapping points (7, 8) being connected respectively to the suction and the pressure intakes (90, 91) of a switch-forming pressostat (9) adapted to trigger a safety event when the difference between the positive and negative pressure values (p+, p-) detected by the air tapping points (8, 7) drops below a determined threshold value.
2. A safety system according to claim 1, characterized by the fact that the air tapping point (7) which is connected to the suction intake (90) of the pressostat (9) is placed inside a suction chamber (50) whose air inlet section is reduced by a narrowing (51) and/or a filter (500) so as to establish head loss at the reduction and increase the value of the suction in said chamber (50).
3. A safety system according to claim 1 or claim 2, characterized by the fact that said suction device (6) is a centrifugal turbine, mounted to rotate inside a sleeve (4) against which the air flow generated by the turbine is projected, and that the air tapping point (8) connected to the pressure intake (91) of the pressostat (9) is placed on the inside wall of said sleeve (4).
4. A safety system according to any one of claims 1 to 3, characterized by the fact that said suction device (6) is a dual turbine, comprising a top set of blades (61) and a bottom set of blades (62), and that the air tapping point which is connected to the pressure intake (91) of the pressostat is placed above the top set of blades (61).
5. A safety system according to claim 3 or claim 4, characterized by the fact that said turbine is mounted at the bottom end of a vertical outlet shaft (30) of an electric motor (3) housed inside a suction chamber (50) in which the air flow travels downwards, the system being characterized by the fact that the air tapping point (7) which is connected to the suction intake (90) of the pressostat (9) is placed in said chamber (50).
6. A safety system according to any one of claims 1 to 5, associated with a duct (1) which exhausts flue gases coming from at least one boiler, the system being characterized by the fact that the pressostat (9) is adapted to cause the boiler to be turned off.
7. A safety system according to any one of claims 1 to 5, associated with a bathroom ventilation duct (1) of a dwelling in which other rooms possess at least one other duct fitted with a similar extractor possessing a motor-driven mechanical extractor device, the system being characterized by the fact that the pressostat (9) is adapted to switch off said motor.

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