EP0054504B1 - Piezoelectric ignition system for a safety gas burner and apparatuses, in particular absorption refrigerators, using such a system - Google Patents

Description

The present invention relates to a gas burner ignition system, combining on the one hand a temperature sensitive safety valve and on the other hand a piezoelectric mechanism. Such systems, well known in the art, can be used on various gas appliances, such as water heaters, heating stoves, absorption refrigerators.

By thermo-sensitive safety valve, in the sense of the present invention, it is necessary to understand a valve with inlet (connected to a gas source), and outlet (connected directly or indirectly to a burner), comprising within it a thermo element -sensitive (itself connected to a sensor arranged so as to be in contact with the burner flame), as well as an elastically charged pusher, making it possible to open the valve at least partially, in the absence of excitation of the thermosensitive element; when the burner is operating, it is the heat-sensitive element which keeps the valve open, the pusher then being released to return to its initial position, under the effect of its elastic load; when the burner stops working, the heat-sensitive element no longer acts, which leads to the automatic closing of the valve. Most often the thermosensitive element and the sensor consist respectively of an electromagnet and a thermoelectric couple.

By piezoelectric mechanism, within the meaning of the present invention, it is necessary to understand a compact system, with electrical outlet (connected to an electrode arranged so as to ignite by sparks the gaseous mixture leaving the burner, the rest of the mechanism being at the mass), comprising within it a piezoelectric ceramic, as well as an elastically charged thrust member making it possible, from the start or during its stroke, to generate by action on the piezoelectric ceramic a high electric voltage (which generates at least one spark between the electrode and the burner); when the thrust member is released, it returns to its initial position, under the effect of its elastic load. Such mechanisms can be single-spark (percussion) or multi-spark (compression). In order to simplify the handling of the ignition systems envisaged by the present invention, in accordance with “document FR-A-2437575” “(deposit number” 78 28317 of 09/27/78) filed by the Applicant, it has already been proposed to assemble the safety valve and the piezoelectric mechanism according to a relative arrangement, for example alignment, in which a single actuation means makes it possible to act, for example in translation, successively on the pusher of the safety valve and on the piezoelectric mechanism pushing member, resetting, or returning to the initial position of the single actuating means, taking place after release under the sole effect of the elastic loads thus released, available in the safety valve and the piezoelectric mechanism.

This solution leads to placing the safety valve and the piezoelectric mechanism in a fixed manner relative to each other, and to providing a relatively complex actuation means, both in its construction and in its operation to act successively. on the safety valve and on the piezoelectric mechanism. This complexity can in certain cases hamper the normal operation of the safety valve, for example by preventing the return of the pusher to its rest position, which is obviously not desirable in the event of the burner going out.

All this leads to wanting to further simplify the ignition systems envisaged by the present invention, so as to make them easily achievable on an industrial level, and perfectly reliable in terms of their daily use, domestic for example. This is the technical problem which the present invention aims to solve.

According to the present invention, on the one hand the actuating means is integral with the pushing member of the piezoelectric mechanism, which by its part opposite to said pushing member cooperates with the pusher, the safety valve, and d on the other hand the force required to actuate the piezoelectric mechanism is greater than the force required to at least partially open the safety valve by means of the pusher.

By actuation means integral with the pushing member of the piezoelectric mechanism, it should be understood that either the actuation means, push button for example, is identified with the pushing member in question, or the same means is distinct from the same member and connected to the latter, for example in rotation, the actuating means being capable of rotating relative to the thrust member of the piezoelectric mechanism.

By cooperation of the piezoelectric mechanism with the pusher of the safety valve, it should be understood that the part of the mechanism, opposite to the thrust member acts under the effect of the actuating means, either indirectly, for example thanks to an intermediate mechanical means transmitting the thrust exerted on the mechanism to the valve pusher, either directly, for example by pressing against the pusher of the same valve.

By force necessary for actuating the piezoelectric mechanism is meant the value of the thrust from which the piezoelectric mechanism is actuated or triggered, and therefore at least one electric shock is produced. Thus in the case of a piezoelectric percussion mechanism, the thrust exerted on the thrust member increases with the displacement of the latter, in particular as a function of the deflection imposed on the elastic return load (spring in

general); past a certain value of this thrust, the striker is projected, under the effect of its own elastic load, against the piezoelectric ceramic, and it is this value which should be retained as being the force necessary for the actuation of the piezoelectric mechanism. By force necessary to at least partially open the safety valve is meant the value of the thrust exerted on the pusher, making it possible to at least partially open said valve, and ensuring the passage of a gas flow at least sufficient to ignition of the burner, with which said valve communicates.

As before, the thrust exerted on the pusher of the safety valve increases with the displacement of the latter, in particular as a function of the deflection imposed on the elastic return load (spring in general).

• 1 Fig. 1 représente une vue de dessus d'un système d'allumage conforme à la présente invention, avec coupe partielle, la vanne de sécurité et le mécanisme piézo-électrique étant en position de repos.
• Fig. 2 représente une vue en perspective, avec arrachements partiels, du mécanisme piézo-électrique faisant partie du système conforme à la fig. 1.

The appended drawing, given by way of example, will allow a better understanding of the invention, the characteristics which it presents and the advantages which it is capable of providing:

• 1 Fig. 1 shows a top view of an ignition system according to the present invention, with partial section, the safety valve and the piezoelectric mechanism being in the rest position.
• Fig. 2 shows a perspective view, with partial cutaway, of the piezoelectric mechanism forming part of the system according to FIG. 1.

A security system in accordance with the invention brings together, behind and against each other, an actuating means 1, a piezoelectric mechanism 2, and a safety valve 3. The safety valve is retained by two brackets 4 and 5, the vertical wing of which has an orifice adjusted to receive the body 6 of the safety valve. The safety valve is blocked on the support constituted by the two brackets 4 and 5 is effected on the one hand by the shouldered nut 7 bearing against the bracket 5, and on the other hand by a ring of stop 8 forcibly mounted on the other side of the same bracket. An intermediate piece 9 encloses the piezoelectric mechanism, and the pushing member 10 belonging to the latter freely exits from this piece. The actuating means, or push button 1, consists of two differently colored parts 11 and 12, fitted one on the other. The push button 1 is fixed to the pushing member 10 of the mechanism 2, by means of a screw 13 retaining the part 11 of the actuating means 1. The rear part of the intermediate part 9, opposite to the the pushing member 10 is fixed to the pusher 14 of the safety valve 3, for example by means of a clip 15, which is received in two slots provided on the part 9 and a circular groove provided on the pusher 14. Thus, the rear part of the mechanism 2, opposite the pushing member 10, is constantly in abutment against the push-button 14 of the valve 3. An angle iron 16 having a flared orifice 17 serves as a guide for the push-button 1.

In accordance with fig. 2, in a manner known per se, the piezoelectric mechanism comprises a housing 18, the thrust member 10, movable in translation, being capable of sinking into the housing. A piezoelectric ceramic 19 is contained in the housing 18. The displacement of the thrust member 10 in the housing 18 makes it possible both to load a return spring 20, and to project in translation a striker 21 against the ceramic 19 , under the effect of another spring 22, previously loaded during the same movement of the thrust member 10; the percussion is triggered when the lug 23 integral with the striker 21 escapes from its housing 24 provided on the housing 18, under the effect of the ramp 25 provided on the thrust member 10. The return to the initial position of the thrust member 10 and striker 21 takes place under the sole effect of the return spring 20, the counter-ramp 26 provided on the member 10 bringing the lug 23 back into its housing 24.

From the description of both the constitution and the operation of the piezoelectric mechanism 2, it follows that the force necessary for its actuation is equal to the sum of the elastic load of the spring 20 and that of the spring 22, when the lug 23 leaves its housing 24, that is to say approximately at the end of the travel of the pushing member 10.

In accordance with fig. 1, the safety valve 3 comprises the tubular body 6, the end opposite the nut 7 is associated with the pusher 14, loaded elastically towards the outside by a compression spring 27. The interior end of the pusher 14 has a rod 28 capable of acting on a valve 29 pushed against its seat 6a by means of another spring 30. A heat-sensitive element 31, for example an electromagnet, keeps the valve 29 open if the sensor (not shown) ) connected to it by a wire 32, reaches a determined temperature.

The pusher 14 can be maintained in an intermediate position, thanks to the presence of balls 33 loaded centrifugally and cooperating with a chamfer 6b of the body. Of course, the safety valve is provided with a gas inlet 34 (about) located upstream of the valve 29, and a gas outlet 35 located downstream of the valve.

According to the preceding description of the arrangement and operation of the safety valve, the force necessary to open it at least partially by means of the pusher 14, that is to say the force necessary to move the valve 29 and reach between the latter and the seat a passage section sufficient to ignite the burner, is approximately equal to the elastic load of the spring 27, plus the elastic load of the spring 30, when said sufficient passage section is reached. According to the invention, it is this force which must remain less than the actuation force of the piezoelectric mechanism.

• - Dans une première partie de la course, on enfonce le poussoir 14 de la vanne de sécurité 3 sans enfoncer l'organe de poussée 10 du mécanisme piézo-électrique 2; à la fin de cette première partie, la poussée exercée sur le bouton-poussoir 1 atteint la force nécessaire pour ouvrir au moins partiellement la vanne de sécurité;
• - Dans une deuxième partie de la course, la poussée exercée dépasse la force précitée, et on enfonce alors l'organe de poussée 10 du mécanisme 2, tout en maintenant enfoncé ou en continuant d'enfoncer le poussoir 14 de la vanne 3; à la fin de cette deuxième partie, la poussée exercée sur le bouton-poussoir 1 atteint la force d'actionnement du mécanisme piézo-électrique; on provoque alors une étincelle au brûleur, via le câble 36 relié à la céramique 19;
• - Lorsqu'on relâche le bouton-poussoir 1, l'organe de poussée 10 du mécanisme 2, et le poussoir 14 de la vanne 3 co-agissent, sous l'effet de leurs charges élastiques respectives, devenues libres, pour ramener le bouton-poussoir 1, soit dans une position intermédiaire, correspondant à la retenue du poussoir 14 sur l'épaulement 6b de la vanne de sécurité, dans laquelle la partie 11 est cachée par la cornière 16, soit dans la position initiale, si la flame du brûleur n'est pas allumée, position dans laquelle les deux parties 11 et 12 du bouton-poussoir 1 sont visibles.

The operation of the ignition system according to the invention is essentially the following, starting from the rest position of FIG. 1, and in gradually pressing push-button 1:

• - In a first part of the stroke, the pusher 14 of the safety valve 3 is depressed without depressing the thrust member 10 of the piezoelectric mechanism 2; at the end of this first part, the thrust exerted on the push-button 1 reaches the force necessary to at least partially open the safety valve;
• - In a second part of the stroke, the thrust exerted exceeds the aforementioned force, and then pushes the pushing member 10 of the mechanism 2, while holding down or continuing to push the plunger 14 of the valve 3; at the end of this second part, the thrust exerted on the push button 1 reaches the actuating force of the piezoelectric mechanism; a spark is then caused to the burner, via the cable 36 connected to the ceramic 19;
• - When the push-button 1 is released, the pushing member 10 of the mechanism 2, and the push-button 14 of the valve 3 co-act, under the effect of their respective elastic loads, which have become free, to bring the button back -pusher 1, either in an intermediate position, corresponding to the retention of the pusher 14 on the shoulder 6b of the safety valve, in which the part 11 is hidden by the angle 16, or in the initial position, if the flame of the burner is not lit, position in which the two parts 11 and 12 of the push button 1 are visible.

The invention applies to any gas burner appliance, in particular absorption refrigerators equipped with such a burner.

Claims (8)

1. Piezo-electric lighting system for a gas burner with safety device, comprising:

- a thermo-sensitive safety shutter (3), with a resiliently mounted push-member (14), allowing the shutter to be opened when the burner is not lit;

- a piezo-electric mechanism (2) comprising a resiliently mounted pressure member (10);

- a single actuating means (1), for actuating the push-member (1) of the safety shutter (3) and then the pressure member (10) of the piezo-electric mechanism (2), the re-setting of the actuating means (14) taking place under the sole effect of the resilience of the safety shutter (3) and the piezo-electric mechanism (2), characterized in that the actuating means (1) is integral with the pressure member (10) of the piezo-electric mechanism (2), the part of the latter opposed to the said pressure member (10) cooperating with the push-member (14) of the safety shutter (3), and in that the force necessary to actuate the piezo-electric mechanism (2) is greater than the force necessary to open at least partially the safety shutter (3), by means of the push-member (14).

2. System according to Claim 1, characterized in that the actuating means (1) is separate from the pressure member (10) and is fixed on the latter. r.

3. System according to Claim 1, characterized in that the part of the piezo-electric mechanism (2) opposed to the pressure member (10) is supported by the push-member (14) of the safety shutter (3).

4. System according to Claim 3, characterized in that an intermediate piece (9) connects, on the one hand the part (18) of the piezo-electric mechanism (2) opposed to the pressure member (10), and on the other hand the push-member (14) of the safety shutter (3).

5. System according to Claim 1, characterized in that the actuating means (1) cooperates with a guiding means (17).

6. System according to Claim 1, characterized in that the actuating means (1), the piezo-electric mechanism (2) and the safety shutter (3) are aligned with and to each other.

7. Apparatus comprising a gas burner, characterized in that it is provided with a lighting system according to any one of claims 1 to 6.

8. Absorption refrigerator with a gas burner, characterized in that it is provided with a lighting system according to any one of claims 1 to 6.

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