EP1291580A1 - Gas appliance with a burner in the lower part and with security means, and its use as a water heater - Google Patents

Abstract

The gas burner (4) is in the bottom part of the equipment and near to an underlying surface (6). There is an atmosphere pilot light control temperature detector (12) connected to the gas burner supply with a primary air inlet orifice to which is connected a tube (10) whose free orifice (11) is located under the gas burner. The pilot flame (15) temperature detector is coupled to the burner gas supply cut off valve (14). An Independent claim is included for a water gas heater.

Description

The present invention relates to improvements brought to gas appliances, and in particular to water heaters gas, comprising a gas burner arranged in the lower part of said device and in the vicinity of a surface underlying this device, which further comprises a pilot light control of the atmosphere connected to the gas supply of the burner and means for detecting the temperature of the flame of said pilot which are functionally coupled to means for cutting off the gas supply to the main burner,

In some countries (notably North America: USA and Canada), gas water heaters / bath heaters of this type not only equip individual dwellings, but also industrial premises such as garages or auto repair shops. In the latter type many accidents were found by unintentional ignition of gasoline vapors projected in the immediate vicinity of the base of the devices, there where the gas burner is.

To avoid such accidents, the devices have been modified and fitted with explosion-proof screens in front of primary air inlets necessary for the operation of the burner. However, this solution is not satisfactory: given the dirty and dusty environment in the places where the devices are installed, the screens, which must be fairly fine mesh, foul relatively quickly and brake the air supply primary: this results in a sharp increase in the rate of CO and a serious risk of suffocation.

In other cases, the devices have been fitted out with sealed combustion chambers supplied with air primary by vertical pipes with inlet ports are raised above the surface (usually the ground) on which the device rests and on which the essence liquid may spill with formation above stagnant gasoline vapors. Again, this solution is not not satisfactory because it requires a modification of the basic structure of the devices.

The object of the invention is to propose a solution particularly effective in terms of security, which accommodates a dirty environment, which does not requires no modification of the basic structure of devices and which, therefore, can apply not only new devices, but also existing devices by a simple modification, and which ultimately does not entail not too high an additional cost.

For these purposes, a gas appliance as mentioned in preamble, is characterized, being arranged in accordance with the invention, in that the atmosphere control pilot light has a primary air intake port to which connected a tube whose free orifice is located below the level of the gas burner.

Thanks to such an arrangement, the gas supply to the main burner is interrupted when the means of temperature detection detect a cooling of the pilot flame which is caused by enrichment in mixture gas (presence of vapors in primary air or obstruction of the air supply by a liquid phase, especially liquid petrol).

Preferably, the free orifice of said tube is located in close proximity to the support surface of the device, i.e. it is located as close as possible from this surface in order to be assured that the safety device will act as soon as vapors and / or a liquid (essence) will appear on the underlying surface, while still leaving enough space for the primary air intake can be done in quantity sufficient and the pilot can operate normally in the absence of petrol. In particular, in a usual installation mode, the appliance rests on the floor and the free end of the tube is then located near immediately from the ground.

In a simple embodiment, the means of flame temperature detection include at minus one thermocouple which is arranged in the axis and downstream of the pilot light and whose output voltage controls them means for cutting off the gas supply to the burner main.

In an efficient embodiment allowing overcoming the influence of ambient temperature, flame temperature detection means include two thermocouples, the second of the thermocouples can be offset laterally from the axis of the pilot light, and are capable of generating an output voltage not zero in the presence of a flame resulting from operation correct pilot light and output voltage substantially zero in the absence of flame or in the presence an abnormal flame due to gas enrichment of the mixing, and in that the cut-off means of the gas supply are of the opening type in the presence of a non-zero and closing control electric voltage in the presence of a zero control electric voltage.

In another embodiment which allows collect sufficient voltage to excite means for controlling the gas supply to the burner main, it is expected that the means for detecting the flame temperature further include a thermal effect microswitch, which can be arranged laterally offset from the pilot axis, which has an input terminal connected to an electrical source and an output terminal connected to the control means the gas supply to the main burner, and which has a excitation input terminal connected to the above thermocouple (12), that said microswitch is capable of generating a output voltage equal to supply voltage when excited by the thermocouple brought into contact flame resulting from proper operation of the pilot light and zero output voltage in the absence of flame or in the presence of an abnormal flame due to a gas enrichment of the mixture, and that the means of gas supply controls are of the opening type in the presence of a non-zero control electric voltage and closing in the presence of an electrical voltage of null order.

In an alternative embodiment suitable for preventing an accidental shutdown of the main burner, provision is made between the second thermocouple or the microswitch and the night light is interposed a mobile screen sensitive to a temperature rise so that said screen remains in position in the presence of a stable flame or briefly extended to prevent tripping inadvertent said second thermocouple or microswitch and to prevent an inadvertent interruption of the supply by gas, but that said screen is moved under the action of a overheating due to a long-lasting flame and then puts said second thermocouple or microswitch in presence of said elongated flame with a view to cutting off the gas supply. The screen can then advantageously be made up of a bimetallic strip.

As is clear from the explanations which above, the provisions of the invention find a particularly interesting application, although not exclusive, in gas water heaters.

• la figure 1 est une vue schématique en coupe d'un appareil à gaz aménagé conformément à l'invention ;
• les figures 2A à 2C sont des schémas illustrant les moyens de sécurité incorporés selon l'invention dans l'appareil de la figure 1 et montrés dans respectivement trois configurations fonctionnelles différentes ;
• les figures 3A à 3C sont des schémas illustrant un autre mode de réalisation avantageux des moyens de sécurité incorporés dans l'appareil de la figure 1 et montrés dans, respectivement, trois configurations fonctionnelles différentes ;
• la figure 4 est un schéma illustrant une variante de réalisation très simple et très économique constituant une alternative au montage de la figure 3A ;
• les figures 5A à 5C sont des schémas illustrant encore un autre mode de réalisation avantageux des moyens de sécurité incorporés dans l'appareil de la figure 1 et montrés, respectivement, dans trois configurations fonctionnelles différentes ; et
• les figures 6A à 6C sont des schémas illustrant une variante intéressante de réalisation des moyens mis en oeuvre aux figures 3A-3C et 5A-5C.

The invention will be better understood on reading the following detailed description of a preferred embodiment of the invention given solely by way of non-limiting example. In this description, reference is made to the appended drawings in which:

• Figure 1 is a schematic sectional view of a gas appliance arranged in accordance with the invention;
• FIGS. 2A to 2C are diagrams illustrating the safety means incorporated according to the invention in the apparatus of FIG. 1 and shown in three different functional configurations respectively;
• FIGS. 3A to 3C are diagrams illustrating another advantageous embodiment of the security means incorporated in the device of FIG. 1 and shown in, respectively, three different functional configurations;
• Figure 4 is a diagram illustrating a very simple and very economical alternative embodiment constituting an alternative to the assembly of Figure 3A;
• FIGS. 5A to 5C are diagrams illustrating yet another advantageous embodiment of the security means incorporated in the device of FIG. 1 and shown, respectively, in three different functional configurations; and
• Figures 6A to 6C are diagrams illustrating an interesting alternative embodiment of the means used in Figures 3A-3C and 5A-5C.

Referring first to Figure 1, a gas appliance of the type targeted by the invention is shown in the form of a gas water heater 1, since it is there of a preferred, although not exclusive, application provisions of the invention.

The water heater 1 comprises, very succinctly, a outer casing or box 2 forming a covering and containing a water tank 3 at the base of which is located at least one gas burner 4. Above the burner 4 extends a chimney 5 for evacuating the combustion gases, which passes vertically through the water tank 3 and opens the atmosphere at the top of the box 2.

Box 2 is mounted or supported in such a way that its bottom is in the vicinity of an underlying surface 6. For example, in practice, box 2 is based on a support surface such as soil 6 using a base 7 of relatively low height so that the gas burner 4 is found relatively close to this support surface.

The bottom 8 of the body 2 is open, or has openings for the free passage of ambient air by direction of burner 4 (primary air).

We therefore understand that, if a liquid easily evaporable and highly flammable such as petrol projected onto the ground 6 in the immediate vicinity of the apparatus 1 or under it, all the conditions are met for only petrol vapors, or even drops of petrol liquid are entrained with the primary air until burner and dangerously modify the conditions of operation of it.

In the basic structure that has just been described, the device 1 also includes a safety device comprising an atmosphere control pilot light 9, connected to the gas supply to burner 4, which comprises a primary air inlet port to which is connected a air intake tube 10 whose free end 11 is located below the level of the gas burner 4. In addition, assistant to the pilot 9 of the means 12 for detecting the temperature of the flame 15 of the pilot light 9, these means 12 being functionally coupled 13 to cut-off means 14 (motorized tap for example) of the gas supply main burner 4.

In a simple and effective manner, the means 12 of pilot flame detection 12 consist of a thermocouple whose threshold is set in relation to the temperature of flame 13 of the pilot light in normal operation, i.e. when the pilot light is supplied with pure primary air.

So that the operation of the safety device is effective, it is desirable that it interrupt the burner 4 operation as soon as the first appear gasoline vapors or the first traces of liquid gasoline. For this, it is preferable that the orifice 11 of the tube of air intake 10 is located as close as possible to the support surface 6, taking care, however, that sufficient free passage remains so that, in operation normal, air can easily enter the tube in sufficient quantity, so that the burner 4 is normally supplied with primary air and operates correctly.

The safety device implemented according to the invention operates as follows.

In normal operation (Figure 2A), clean air is sucked through the orifice 11 of the tube 10 and the pilot 9 delivers a flame 15 directed axially and having a temperature predetermined which is detected by the thermocouple 12. This, given its threshold setting, delivers a signal which, via line 13, controls the maintenance at the opening of the gas supply cut-off means 14 main burner 4.

If petrol vapors appear 16 (figure 2B, on which the petrol vapors are shown diagrammatically by points), these vapors 16 are entrained with the air by the orifice 11 of the tube 10. The presence of gasoline vapors in the pilot 9 causes a modification of the reports of air and gas with a noticeable weakening of the volume air. This results in significant cooling of the flame temperature 15 'of the pilot light. This flame cooling is immediately detected by thermocouple 12 which then emits a commanding signal then the closure of the gas supply cut-off means 14 main burner 4.

In the presence of liquid gasoline 17 (fig. 2C, on which the liquid essence is represented by dashes), this liquid clogs the orifice 11 of the tube 10 and the air does not no longer reaches pilot 9. Deprived of oxygen, the flame 15 "of the pilot light deforms and no longer heats the thermocouple 12. Immediately, this emits a signal controlling the closing of the switching means 14 gas supply to the main burner 4.

Interestingly, the cutting means 14 gas supply can be made up as a multi-functional tap or valve with control electromagnetic which is sensitive to electromotive force generated by thermocouple 12.

The single thermocouple embodiment 12 illustrated in FIGS. 2A to 2C presents a very large sensitivity to variations in ambient temperature. Such layout, which has the advantage of simplicity, can give complete satisfaction in a temperature environment stable. On the other hand, in an atmosphere with temperature variable, it is better to use the layout illustrated in Figures 3A and 3C which then turns out to be more advantageous because, operating differently, it frees itself from thermal drifts.

In this sophisticated arrangement, the thermocouple 12A which is arranged in the axis of the pilot and whose electrical output is connected at 13 to the input positive (or non-inverting input) of a device electronic comparator 18.

We add a second thermocouple 12B (which can advantageously be provided with a protective sleeve in ceramic 19 to dampen the convections of heat returned possible for example by a movement of the flame 15 of the pilot under the effect of a draft) which is arranged more distant and offset from the axis of the pilot. The electrical output of thermocouple 12B is connected at 20 to the negative input (or inverting input) of the comparator device 18.

Finally, the output of the comparator device 18 is connected at 21 to the control of the switching means gas supply 14, advantageously constituted under electromagnetic valve, which are inserted in the gas supply pipe 22 to the burner gas 4. Preferably, for safety reasons the valve 14 has a positive opening control, i.e. that it is in the open position when a voltage not null is applied to its command input and it is automatically recalled to the closed position within other cases (zero control voltage; no voltage control).

The operation of this embodiment is the next.

In normal operation (FIG. 3A), the primary air is correctly sucked towards the pilot 9 through the tube 10 and the flame 15, having a normal temperature, bathes the sensitive part of the thermocouple 12A; the latter then delivers a positive voltage V _A (for example typically 9 mV) applied to the positive input of the comparator device 18. For its part, the thermocouple 12B is not touched by the flame and it delivers a voltage V _B which is substantially zero at the inverting input of the comparator device 18. Under these conditions, the comparator device 18 delivers an output voltage V _s which is substantially equal to the input voltage V _A present on its positive terminal, voltage output which is applied to the control input terminal of the valve 14 and which maintains the latter in the open position. The gas therefore flows (arrow 23) in the direction of the burner 4.

If gasoline vapors 16 are present at the orifice 16 of the tube 10 and are drawn into it (FIG. 3B), this results in a cooling of the flame which lengthens and softens: henceforth, not only the flame 15 'bathes the thermocouple 12A, but it also bathes the thermocouple 12B. Under these conditions, the two thermocouples deliver voltages V _A and V _{B, which are} substantially identical (for example typically 0.9 mV) which are applied to the non-inverting and inverting inputs of the comparator device 18 respectively. As a result, the voltage of output V _s of the comparator device 18 is substantially zero. As the valve 14 control is no longer energized, the valve closes and interrupts the gas supply to burner 4.

In the case of the presence of a liquid (in particular of liquid essence) obstructing the tube 10 (FIG. 3C), the flame deprived of air is shortened and is deflected (15 "), so that it does not bathe then neither of the two thermocouples 12A, 12B. These deliver output voltages V _A and V _B which are zero; the comparator device 18 therefore also delivers an output voltage which is zero. not energized, the valve closes and interrupts the gas supply to the burner 4.

In the presence of a variation in the ambient temperature causing a drift (assumed to be substantially identical) of the output voltages of the two thermocouples 12A, 12B, the differential function introduced by the comparator device eliminates the terms of drift and the output signal V _s is insensitive to this thermal influence.

We can constitute an order identical to what has just been described with reference to FIGS. 3A to 3D by putting using much simpler means as illustrated in figure 4. This simple assembly uses at the same thermocouples 12A and 12B as before, but these are connected to each other in series and in opposition so that their respective signals get subtract. Thus the two respective negative terminals of two thermocouples are joined to each other (line 22), while the positive terminals of the main thermocouple 12A and 12B thermocouple, respectively, are connected (24, 25) to the electromagnetic control of valve 14. The combinations of signals from thermocouples 12A, 12B, and therefore the conditions for opening / closing tap 14 are same as those indicated above with regard to the figures 3A to 3C.

Although the means described above with reference to FIGS. 3A-3C give all satisfaction with regard to operating safety, they nevertheless have the drawback that the output voltage V _s delivered by the thermocouples is relatively low (for example typically of from 5 to 10 mV). As a result, for reliable operation, the means 14 for cutting off the gas supply which are of the electromagnetic type must be equipped with a high-performance, well-designed and therefore expensive coil. Certain manufacturers, who wish to lower the manufacturing cost of the devices as much as possible, have expressed the desire to use low-performance, but inexpensive coils, which require a significantly higher excitation voltage than that which can be delivered by thermocouples.

To meet this demand jointly with same security requirements as before, we can have use of the assembly illustrated in FIGS. 5A-5C, on which we used the same reference numbers than in Figures 3A-3C to designate identical members. An effect microswitch 26 is added to the thermocouple 12 thermal (i.e. thermal contact reversal) which can be arranged laterally offset from the axis of the pilot light 9. The output of the thermocouple 12 is connected by line 13 to an excitation input of the microswitch 26. Furthermore, microswitch 26 has a main input terminal connected to a voltage source V and an output which is connected by line 21 to the means 14 for gas supply cut-off control.

In normal operation (FIG. 5A), the flame 15 bathes the sensitive part of the thermocouple 12 without reaching the microswitch 26. The voltage V _A delivered by the thermocouple 12 maintains the microswitch 26 in a conduction state between its main input and its output. so that the output voltage V _s is equal to the voltage V of the source. It is therefore under the voltage V that the gas supply control means 14 are excited, which, as indicated above, are maintained in the open position (supply to the main burner) in the presence of a voltage of excitation. With this arrangement, the gas supply control means 14 can be energized under a voltage V of any value, even high, independently of the voltage V _A delivered by the thermocouple. The microswitch 26 then behaves like a relay.

If gasoline vapors 16 are present at the orifice 16 of the tube 10 and are drawn into it (FIG. 5B), this results in a cooling of the flame which lengthens and softens: the flame 15 ′ bathes the thermocouple 12, but also reaches the microswitch 26. The latter, being of thermal effect, switches under the effect of the increase in temperature and opens the electrical excitation circuit of the means 14 for controlling the supply of gas (V _s = 0): the valve closes and interrupts the gas supply to the main burner.

In the case of the presence of a liquid (in particular of liquid gasoline) blocking the orifice 10 (FIG. 3C), the flame deprived of air is shortened and is deflected (flame 15 "): the thermocouple 12, n ' being more heated, then delivers a voltage V _A which is zero or at least too low to excite the microswitch 26. The latter is then positioned in the open position (V _s = 0) and the means 14 for controlling gas supply, no longer energized, bring the valve to the closed position, interrupting the gas supply to the main burner.

In the embodiments which have just been exposed with reference to FIGS. 3A-3C and 5A-5C, the second thermocouple 12B or microswitch 26 are sensitive to an extension of the flame and then command closure the main burner supply valve. To avoid an untimely stop of the operation of the device in the case of a short-term disturbance resulting in a fugitive extension of the pilot flame, we suggest to use the arrangement illustrated in Figures 6A-6C (which corresponds to the embodiment of FIGS. 5A-5C, but which can be renewed as for other modes of embodiment, in particular that of FIGS. 3A-3C).

It is planned to interpose, between the pilot 9 and the microswitch 26, a mobile screen 27 which can only be erased presence of non-fugitive temperature rise caused by a long-lasting flame due to a pilot light failure. Such a screen 27 can advantageously be constituted, in a simple manner, by a bimetallic strip as illustrated in FIG. 6A.

The bimetallic strip forming the screen 27 is arranged so that during normal operation of the pilot light, it either not reached by the flame 15 bathing the thermocouple 12, but either as an extension of the flame 15 beyond this. The microswitch 26 then operates under the conditions set out above with regard to the Figure 5A.

If, for a fortuitous reason, the flame lengthens briefly (flame 15 ₁ in FIG. 6B), it certainly reaches the screen 27; but it does not have time to heat up and does not move / deform. The microswitch 26, thus protected, does not switch and maintains the continuity of the excitation circuit of the means 14 for controlling the supply of gas to the main burner (arrow 23).

On the other hand, in the presence of a flame 15 'elongated by sustainably due to the presence of fuel in the air intake tube 10, the bimetallic strip constituting the screen 27 is deformed by releasing the microswitch 26 which also becomes exposed to the 15 'flame (Figure 6C). The microswitch 26, heated, cut the excitation circuit of the control means 14 gas supply and the tap closes, within conditions set out above with reference to FIG. 5B.

Claims (9)

Gas appliance (1), comprising a gas burner (4) disposed in the lower part of said appliance and in the vicinity of a surface (6) underlying this appliance, which further comprises an atmosphere control pilot light ( 12) connected to the gas supply to the burner and means (12) for detecting the flame temperature (15) of said pilot which are functionally coupled to means (14) for cutting off the gas supply to the main burner (4),
characterized in that the atmosphere control pilot light has a primary air inlet port to which a tube (10) is connected, the free port (11) of which is located below the level of the gas burner (4) ,
whereby the gas supply to the main burner is interrupted when the temperature detection means detect a cooling of the pilot flame which is caused by a gas enrichment of the mixture (presence of vapors in the primary air or obstruction of the air supply by a liquid phase). Apparatus according to claim 1, characterized in that the free orifice (11) of said air suction tube (10) is located in the immediate vicinity of the surface (6) underlying the apparatus. Apparatus according to claim 2, characterized in that it rests on the ground (6) and in that the free orifice (11) of the air suction tube (10) is located in the immediate vicinity of the ground (6 ). Apparatus according to any one of claims 1 to 3, characterized in that the flame temperature detection means comprise at least one thermocouple (12) which is arranged in the axis and downstream of the pilot and whose output voltage controls the means for cutting off the gas supply to the main burner (4). Gas appliance according to claim 4,
characterized in that the flame temperature detection means comprise two thermocouples (12A, 12B), the second of the thermocouples (12B) being able to be offset laterally with respect to the axis of the pilot, and are capable of generating a non-zero output voltage (V _s ) in the presence of a flame (15) resulting from correct operation of the pilot light and a substantially zero output voltage (V _s ) in the absence of a flame or in the presence of a abnormal flame (15 ′, 15 ″) due to a gas enrichment of the mixture, and in that the means for cutting off the gas supply (14) are of the opening type in the presence of an electrical control voltage not zero and closing in the presence of a zero control electric voltage. Gas appliance according to claim 4,
characterized in that the flame temperature detection means further comprises a thermal effect microswitch (26), which can be arranged laterally offset with respect to the axis of the pilot (9), which has a terminal d input connected to an electrical source (V) and an output terminal connected to the means (14) for controlling the gas supply to the main burner, and which has an excitation input terminal connected to the above thermocouple (12 )
in that said microswitch (26) is capable of generating an output voltage (V _s ) equal to the supply voltage (V) when it is excited by the thermocouple (12) placed in the presence of a flame (15 ) resulting from correct operation of the pilot light (9) and a zero output voltage (V _s ) in the absence of a flame or in the presence of an abnormal flame (15 ', 15 ") due to gas enrichment of the mixture, and
in that the means (14) for controlling the gas supply are of the opening type in the presence of a non-zero electrical control voltage and closing in the presence of a zero electrical control voltage. Gas appliance according to claim 5 or 6,
characterized in that between the second thermocouple (12B) or the microswitch (26) and the pilot light (9) is interposed a mobile screen (27) sensitive to a rise in temperature so that said screen (27) remains in position in the presence of a stable (15) or briefly elongated (15 ₁ ) flame in order to prevent inadvertent triggering of said second thermocouple (12B) or microswitch (26) and to prevent an inadvertent interruption of the gas supply, but that said screen (27) is moved under the action of a heating due to a flame (15 ') elongated in a durable manner and then places said second thermocouple or microswitch in the presence of said elongated flame (15') for the purpose of gas supply cut off. Gas appliance according to claim 7,
characterized in that the mobile screen (27) consists of a bimetallic strip. Gas water heater, characterized in that it is arranged according to any one of Claims 1 to 8.

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