BE1018675A3 - DEVICE FOR DETERMINING A GASEOUS MIXTURE. - Google Patents

Abstract

The invention relates to a device 1 for dosing a mixture of at least two gases, such as, for example, an oxidizing gas and a combustible gas. The ratio between the two gases is controlled through an actuator 5 comprising a motor 8, a reduction gear 10 with a worm and wheel and a conversion mechanism 11 in the form of a transmission with screw 12 and nut 13. The invention also relates to an oven 42 with several zones 43 in communication with each other, with an analyzer 56 of the atmospheric compositions of said zones 43, at least one burner 44 per zone 43, at least metering device 1 according to any one of the preceding claims for the supply of combustible gas and oxidizing gas to at least one burner in each zone, and an electronic regulator 57 connected to said analyzer 56 and to the actuators 5 of said metering devices 1 to maintain in each zone 43 a substantially constant atmospheric composition according to a set point 61.

Description

"Device for dosing a gaseous mixture"

The present invention relates to a device for the metering of a mixture of at least two gases, such as, for example, an oxidizing gas and a fuel gas.

Regulation of the atmospheric composition in an oven, particularly to maintain different compositions in several communicating zones in the oven or to change the composition during a cycle, is a problem common to several technical fields, such as, for example, for example, in: • the production of wire • the production of hollow glass, and • the non-ferrous or reactive metal industries, such as copper, as well as in other areas where atmospheric interactions in multi-zone ovens can influence the treatment of materials.

In the production of metal wires, as disclosed, for example, in the international patent application WO 03/104501, heat treatment steps often take place between the different drawing steps. This heat treatment, called "patenting", is done in two stages, in order to obtain a structure of lamellar layers of perlite allowing either a subsequent drawing or fixing of the ultimate breaking load.

At first, the wire is raised to a temperature of 950 to 1000 ° C. to homogeneously dissolve the carbides and obtain an austenitic type structure. This step is called austenitization.

In a second step, the wire is cooled rapidly to a temperature of 530 to 600 ° C, to be finally maintained at this temperature about 6 to 12 seconds to ensure the precipitation of carbides in lamellar form.

This two-step process is carried out on sheets of yarn passing first through a high temperature furnace, called austenitization furnace, and then through a fluidized bed or molten lead bath. An alternative is to ensure its cooling in air or in an aqueous medium.

During the austenitization step, the wire is raised to high temperatures where the risk of decarburization, that is to say of oxidation on the surface, is important, and all the more so since the wire must be maintained above 850 to 950 ° C to ensure complete dissolution of carbides.

Indeed, the significant oxidation of the wire gives a film which, after pickling, leaves on the surface a carbon-depleted steel, where the desired pearlitic structure is not present.

To avoid this oxidation, either each wire is inserted into a tube heated from the outside in which a protective gas is injected, or the wire is in direct contact with an atmosphere of fixed composition, thus avoiding the oxidation of its surface.

The latter solution is applied in furnaces where the products of combustion are in direct contact with the wires. These ovens are called "bare fire ovens". If it is not possible to prevent the formation of a very small oxide film at the surface, because of the contact of the wire with the residual water of the combustion, this is normally without any negative consequence. On the contrary, a film of a few microns in size is advantageous for ensuring a satisfactory surface condition. However, it is necessary to avoid deep decarburization which would normally be fatal to the treated product.

These furnaces, typically comprising 3 to 5 successive zones, have increasingly reducing atmospheres as the wires reach a high temperature. The atmosphere in these zones is determined by the composition of the fumes leaving the burners, a composition which must vary according to the position of the burner in the oven, and which in turn depends on the air-fuel ratio of the mixture supplied to the burner.

In the production of hollow glasses, such as bottles or beverage glasses, beyond a main melting furnace, there are channel-shaped furnaces in which the glass is slowly cooled to obtain a viscosity compatible with the mold. wherein the glass will be cast. This type of oven is called "feeder" or "forehearth".

In all these furnaces, the composition of the glass must be maintained in very narrow ranges, as well as possibly the degree of oxidation of its ions, which will ultimately determine either the composition of the glass or the color of the glass. after cooling the casting.

In this context, these furnaces being relatively long, several areas of regulation of the atmospheric composition are also provided, areas in which again a constant atmosphere must be maintained, regardless of the level of production.

In the patenting of metal son, at the exit of the furnace treated son, a perfect seal is desired to avoid the reducing atmosphere of the last zone. Indeed, any presence of oxygen in contact with the reducing carbon monoxide at high temperature would give rise to the creation of a flame, with the risk that oxygen free radicals come decarburize the surface of the son. As a result, the combustion fumes present in the furnace move in the opposite direction to the movement of the wires.

But, as the burners modulate according to the required heating power and each zone receives smoke from the next zone, it is normally necessary to maintain a stable load in order to avoid that the atmosphere settings prevailing in the different zones. oven are disturbed.

These disturbances pose indeed significant problems, because the variation in carbon monoxide produced in an area that the volume of carbon monoxide arriving in the previous zone is different. It can therefore result in an instability of the temperature prevailing in each zone, and an inconstant wire surface state with consequent unstable stripping conditions to be managed and the possibility of contaminating during this one the surface of the wire, for example, after passage of the wire in the lead quench tank.

By the same phenomena, in the production of hollow glass, a modification of power on one zone can cause an interference of the atmosphere of this zone on another.

Both in the austenitization furnaces of wire as in these "feeders" for the production of hollow glass, it is known to those skilled in the art to modulate the air-fuel gas ratio with which each burner or group of burners is fed. manually with a proportional horn mixer, as previously disclosed in French patent FR 1.180.156. The set of burners in each zone can be fed by a single mixer, or by several mixers delivering the same air-fuel gas ratio.

For manual modulation of the air-fuel gas ratio with such a mixer, an operator must regularly measure the atmosphere in each zone of the furnace with an analyzer, interpret the results, and move a mixture control member into the mixer accordingly. This involves several factors that are difficult to control, such as the rate and regularity of measurement of the oven atmosphere, the order of analysis of the zones, the use of the analyzer (calibration, reading) and the precision the interpretation of the results obtained, the interpretation of the type of combustion given by, eg a control burner, and the sensitivity of the operator when acting on the mixing control member. The human factor can therefore significantly affect the quality of production. The same problem is even more acute in furnaces with one or more distinct zones, in which the atmospheric composition in each zone must follow a variable setpoint throughout the production cycle.

In order to solve this problem, it is therefore highly desirable to automate the setting of the mixture in the mixers as a function of the difference between the desired atmosphere and the actual atmosphere in each zone of the oven. For this, it is necessary to control the mixers and consequently motorize them.

A motorized mixer has been proposed in Belgian Patent BE 764.407, which seems to us to constitute the closest state of the art. This device for the metering of a mixture of at least two gases, such as, for example, air and a combustible gas, comprising: a first nozzle comprising a convergent portion opening into an outlet, this nozzle communicating upstream said convergent portion with a first conduit for supplying one of said gases; a second nozzle downstream of the first nozzle, substantially coaxial thereto and having at least one converging input portion and a diverging output portion, one of said first or second nozzles being slidably mounted relative to the other, the output the first nozzle can thus be introduced into the inlet of the second; a chamber, into which a second supply line for another of said gases opens, in communication with the outlet of the first nozzle and the inlet of the second; and an actuator comprising: a motor with a rotary output shaft, a reduction gear connected to said rotary shaft for multiplying the rotational movement, and a conversion mechanism with a rotary input connected to said reduction gear and a connected axial output. to the sliding nozzle for converting said downmixed rotational movement into an axial displacement movement of the sliding nozzle.

In this prior art mixer, the gear reduction gear is formed by a straight gear, and the transmission by a rotating ring surrounding the mixer, with an internal thread engaged to an axially guided external thread and connected to the sliding nozzle.

However, unexpectedly, this motorized metering device of the prior art has not found practical applications in the technical fields such as those of the patenting of wire and the production of hollow glass, which require great precision in The mixture. Several disadvantages have been discovered:

First of all, the right gear reduction gear has excessive play for the fine adjustment of the mixture, and in particular for the continuous regulation. In addition, it offers a limited gear ratio and is not self-locking, which therefore requires, in the downstream conversion mechanism, a very low thread angle of the ring and a large thread diameter. to obtain a self-locking actuator allowing a fine displacement of the sliding nozzle. However, such large diameter and small angle threads constitute an additional source of play. The mechanical clearance between the motor and the sliding nozzle thus introduces a hysteresis in the mixture control circuit disturbing the correct setting of the mixture.

In addition, the machining of the internal and external threads, because of their large diameter and small thread angle requires high accuracy, and therefore a high manufacturing cost.

It is advantageous to provide a dosing device for a gaseous mixture allowing automatic regulation with precision and without sensitive hysteresis. For this, the gear reduction gear is a wheel and worm gear.

The use of a worm gear and worm gear as a gear reduction gear allows a much higher gear with a much more limited game. Conversion of the downstream movement can be accomplished without the use of threads with a small thread angle. The total clearance of the actuator is therefore strongly limited, allowing adjustment of the mixture without sensitive hysteresis.

Preferably, said gear reduction gear wheel and worm can be self-locking. In this way, neither the downstream conversion mechanism nor the upstream engine must no longer be self-locking, which further facilitates the realization of the actuator.

Preferably, the metering device may comprise at least one axial slot in a wall, through which a pin connected to the sliding nozzle passes. In this way, the displacement of the sliding nozzle is guided axially and can also be operated and / or measured from the outside. For this, said pin can be connected at least to said transmission to actuate the axial displacement movement of the sliding mounted nozzle and / or to position sensors of said pin, such as, for example, end-of-stroke sensors. .

Preferably, said conversion mechanism may be a screw and nut transmission. Even more preferably, it comprises a non-coaxial screw with said nozzles mounted outside the device. In this way, this transmission can remain easily accessible for maintenance, while having a small footprint. The screw and nut transmission may also comprise a nut at least partially made of synthetic material, which may advantageously have a predetermined maximum breaking load, so as to break in the event of mechanical blocking of the mixer, in the case of non-triggering. electrical protection of the motor, or in the event of a malfunction of a limit switch and ensures the protection of said mixer, while limiting the play of the transmission, and thus the hysteresis of the adjustment of the mixture. In particular, the maximum breaking load of the nut can be less than a maximum load of the motor, so as to protect it against overloads.

Another object of the present invention is to provide an oven with at least one heat treatment zone with an automatically regulated atmosphere. For this, the present invention also relates to an oven comprising at least one heat treatment zone, an analyzer of atmospheric compositions of said at least one zone, at least one burner per zone, at least one metering device according to the invention for supplying oxidizing gas and fuel gas to the at least one burner of each zone, and an electronic regulator connected to said analyzer and the actuators of said metering devices for controlling in each zone an atmospheric composition substantially corresponding to a set point. Thus, a predetermined atmospheric composition, substantially constant or variable according to a cycle, can be controlled in each zone, and this independently of the load of the oven.

Preferably, said electronic regulator may be a PID regulator, which allows a rapid response to deviations from the instructions, while largely avoiding positive feedback effects.

Preferably, said furnace may comprise a plurality of said zones in communication with one another. In this way, the invention makes it possible to prevent the atmospheric composition of an overpressure zone from affecting that of a zone with a lower pressure.

Preferably, said analyzer may comprise oxygen and carbon monoxide sensors, thereby to determine the reducing or oxidizing nature of the atmospheric composition.

Preferably, said analyzer may be in communication with a zone sampling device. Thus, a single analyzer can be used to regulate the atmospheric composition of all areas of the furnace. More preferably, the oven may then also include an extraction pump, and each sampling device a three-way valve, a first is in communication with the corresponding area, a second with said extraction pump, and a third with said analyzer. This ensures the sampling of the atmosphere of each zone for the analyzer. The furnace may also comprise, between said sampling devices and said analyzer, a cooler equipped with an automatic condensate removal pump, in order to provide dry samples of the atmosphere of each zone at a more acceptable temperature for the analyzer. Even more preferably, downstream of said cooler, a moisture detector may be installed to ensure correct operation of the cooler. To ensure the flow of gaseous samples to the analyzer, the furnace may also comprise, between said sampling devices and said analyzer, a pump, preferably connected to a flow meter to ensure a constant flow rate and / or provided with a flow valve. security.

Preferably, the oven may further comprise a device for supplying a calibration gas to the analyzer, to ensure calibration.

Another object of the present invention is that of regulating the atmospheric composition in at least one zone of a combustion furnace. The present invention thus also relates to a method of regulating a metering device according to the invention for supplying oxidizing gas and fuel of at least one burner in at least one zone of the furnace, comprising the following steps: analyzing the atmosphere in said at least one zone; comparing at least one result of said analysis with a setpoint; controlling said motor of the actuator of the device according to a result of said comparison for maintaining the atmospheric composition in said at least one substantially constant zone and in accordance with said setpoint.

Preferably, said engine control can follow a PID regulation law with respect to the result of said comparison.

Preferably, said set point can be substantially constant, in particular in multi-zone furnaces, thus ensuring a constant oxidizing or reducing character in each zone. However, said setpoint could alternatively be variable, following for example a treatment cycle in an oven with one or more zones.

Preferably, in said analysis, at least the relative volumetric contents of said oxygen and carbon monoxide atmosphere can be measured, thereby to determine the oxidizing or reducing nature of said atmosphere.

Another object of the present invention is that of ensuring constant physical properties in products such as metal wires or hollow glass subjected, in scrolling, to a heat treatment in a controlled atmosphere. The present invention thus also relates to the use of a furnace according to the invention as a metal wire patenting furnace, or for the glass treatment between a melting furnace and a mold.

Details of the invention are described below with reference to the drawings.

Figure 1 illustrates in perspective a metering device according to one embodiment of the invention; Figure 2 illustrates the same metering device, in which a bonnet has been removed to expose the actuator; Figure 3 is a detail view of the exposed actuator; Figure 4 is a schematic view of the reduction gear of the actuator of Figure 3; Figure 5 is another perspective view of the device of Figure 1 showing end-of-travel sensors of the sliding nozzle; Figure 6 is a longitudinal section of the device of Figure 1, with the nozzle sliding in a first position; Figure 7 is another longitudinal section of the device of Figure 1, with the sliding nozzle in a second position; FIGS. 8a and 8b are perspective views of a first segment of the device of FIG. 1 comprising the sliding nozzle, without the actuator or the end-of-stroke sensors; Figure 9 is a schematic view of a furnace according to one embodiment of the invention; and Fig. 10 is a diagram of a furnace control method of Fig. 9 in accordance with one embodiment of the invention.

A device for metering a mixture of a first and a second gas, according to an embodiment of the present invention, is illustrated in FIG. 1. This metering device 1 comprises a supply line 2 for the first gas, a supply line 3 for the second gas, an outlet pipe 4 for the mixture, an actuator 5 for adjusting the dosage of the gases in the mixture and covered by a bonnet 6, and end-of-the-end sensors. stroke 7 installed on one side of the metering device 1 transversely opposite the actuator 5.

In FIGS. 2 and 3, the metering device 1 is shown without the bonnet 6. This exposes the actuator 5 which comprises an electric motor 8 with a rotary output shaft 9, a reduction gear 10 connected to said rotary shaft 9 , and a conversion mechanism 11 with a rotary input formed by a screw 12 connected to said reduction gear 10 and an axial outlet formed by a nut 13 engaged on said screw 12. The nut 13 is made of synthetic material, preferably resistant to heat, and is retained in a metal cage 14 on which is fixed a slide 15 of synthetic material, preferably resistant to heat and having a low coefficient of friction with the metal. This slide 15 is guided axially in a groove 16 substantially parallel to the screw 12 and machined on an outer surface of the device 1.

The gear reduction gear 10 is illustrated schematically in FIG. 4. It is a self-locking gear wheel 17 and worm 18, wherein the worm 18 is coupled to the rotary shaft 9 of the motor output 8, and the wheel 17 is coupled to the rotary input of the conversion mechanism 11. Such a wheel and worm gear has the advantage of offering a high gear ratio with a small footprint and especially with a very high clearance. limit.

In an advantageous embodiment, the gear ratio of the down gear 10 of a preferred embodiment of the invention may be 31: 1. With, for example, a pitch of approximately 2.5 mm on the screw 12, this results in an advance of the nut 13 of approximately 8 mm per 100 revolutions of the motor, which facilitates a precise regulation of the position of the nut 13.

By using with this advantageous embodiment a nut 13 with a maximum breaking load of 2.4 kN, and a motor 8 having a maximum torque of approximately 0.25 Nm, that is to say, which can exert a maximum load of approximately 3 kN through said reduction gear 10 and screw 12, the controlled breaking of said nut 13 will protect the motor 8 from overload.

In FIG. 5 it is possible to appreciate the two end-of-travel sensors 7 installed on one side of the device 1 opposite to the actuator 5.

Turning now to Figures 6 and 7, we see the metering device 1 in longitudinal section. It can be appreciated that the metering device 1 comprises three segments 19, 20 and 21. The first segment 19 comprises a sleeve 22 with said delivery line 2 of the first gas, which opens into a first nozzle 23 slidably mounted in this sleeve. 22. This first nozzle 23 has a convergent first portion 24 and a second cylindrical portion 25. Around its outlet end 26, this first nozzle 23 also has a circular outer rim 27. The first nozzle 23 is connected to the metal cage 14 of the nut 13 of the actuator 5 by a pin 28 passing through a slot 29 in the sleeve 22, so that the axial movement of the nut 13 is transmitted to the first nozzle 23. The slide 15 closes the slot 29, thus preventing the first gas from escaping through this slot 29. The first segment 19 comprises also a pin 30 and a slot 31 identical and diametrically opposed to the pin 28 and the slot 29, to indicate the position of the first nozzle 23 to the limit sensors 7. As illustrated in Figures 8a and 8b, this first segment 19 is therefore substantially symmetrical, and the positions of the actuator 5 and the end-of-travel sensors 7 can be exchanged according to the requirements of external dimensions of the device 1.

An annular seal 32 is provided between this first nozzle 23 and the sleeve 22, on either side of the slots 29 and 31. These seals 32 are immobilized in annular housings 33 formed in the outer wall of the first nozzle 23. .

The second section 20 connects the first and third segments 19 and 21, comprises the supply line 3 of the second gas and forms a chamber 34 around the outlet end 26 of the first nozzle 23.

Finally, the third section 21 comprises a second fixed nozzle 35 with a first convergent inlet portion 36, a second cylindrical portion 37, and a third divergent outlet portion 38. This second nozzle 35 thus forms a venturi. The converging portion 36 is formed by two truncated cones 39 and 40 placed end to end. The taper of the first trunk 39 is substantially greater than that of the other trunk 40, which is rather of low conicity.

When the flow rate of the first gas is switched on, the metering device 1 operates as an ejector, in which the jet of the first gas leaving the first nozzle carries with it a proportional flow of the second gas. The metering device 1 makes it possible to obtain a constant ratio of the two gases in a mixture of the latter by maintaining a laminar flow of the coaxial superimposed layers of the two gases in the device, in particular at the moment when the latter are brought into contact with each other. one with the other. The rim 27 makes it possible to create a stationary gas film on the outer wall of the first nozzle 23, thus reducing the friction between this wall and the gas flowing around it. Effective mixing of the two gases takes place only downstream of the metering device 1.

Thus, for a mixture of combustible and oxidant gases, when the metering device 1 is mounted so as to supply a burner or a group of burners, the ratio of the two gases is not influenced by the back pressure. at the burner outlet or burners.

The ratio between the two gases can be adjusted by axial displacement of the first nozzle 23 relative to the second nozzle 35. Because of the convergent shape of the inlet 36, the annular space 41 between the two will decrease when the two nozzles 23 and 35 will be brought together, thereby restricting the flow of the second gas. In FIG. 6, the metering device 1 is illustrated with the first nozzle 23 in its position furthest away from the second nozzle and therefore a maximum ratio between the second and the first gas in the mixture. In Figure 7, however, the first nozzle 23 is advanced to contact the wall of the inlet 36 of the second nozzle 35, thereby closing the annular space 41 to prevent the passage of the second gas.

This displacement of the first nozzle 23 is performed by the actuator 5. When the electric motor 8 rotates the output shaft 9, its rotary motion is first reduced in the gear 10 and then converted into an axial displacement of the The nut 13 and the pin 28 cause the first nozzle 23 in its axial displacement in the sleeve 22, bringing it closer to or away from the second nozzle 35. The ratio between the two gases can thus be adjusted in accordance with FIGS. controlling the engine 8.

Figure 9 schematically shows a furnace 42 having a plurality of zones 43 with regulated atmospheres and in communication with each other. This furnace 42 could be, for example, a wire austenitization furnace moving through the zones 43, or a "feeder" type furnace installed between a main glass melting furnace and a mold to give shape to hollow glasses. In the furnace 42 illustrated, each zone 43 comprises a plurality of burners 44 supplied with fuel gas-air mixture by a metering device 1 such as that disclosed above. However, in order to simplify the diagram, a single burner 44 is illustrated for each zone 43. Each zone 43 also comprises a sampling device 45, making it possible to take gaseous samples from the atmosphere of this zone 43 and comprising a valve 46 to three channels, one of which is in communication with the corresponding zone 43, a second with a common extraction pump 47, and a third with a common pipe 48. On this pipe 48 are installed a device 49 for supplying a calibration gas, a cooler 50 provided with a pump 51 automatic discharge condensate, a humidity detector 52 downstream of the cooler 50 to ensure its correct operation, and a pump 53, provided with a safety valve 54 to avoid a downstream pressure, and connected to a flow meter 55 to ensure a constant flow in the pipe 48. This pipe 48 opens into an analyzer 56 comprising at least sensors of relative volumes of oxygen and carbon monoxide atmospheric samples taken from the zones 43. The analyzer 56 is connected to an electronic regulator 57 to transmit said contents. The electronic regulator 57 is in turn connected to the metering devices 1 in order to adjust by zone the air-fuel mixture with which each burner 44 is fed, and correct it in case the atmospheric composition in the corresponding zone 43 deviates from a prior instruction. This instruction could be adjusted by a user depending on the desired oxidizing or reducing nature of the atmosphere in each zone 43, such as the fuel gas used (eg methane, natural gas, LPG, propane, butane, etc.). and its relation with the oxidizing gas.

The method of regulating the atmospheric composition of each zone 43 of the furnace 42 is illustrated in FIG. 10. When the atmospheric sample taken by the device 45 is supplied, through the pipe 48 with the cooler 50 and the pump 53, to the analyzer 56, which measures its oxygen and carbon monoxide contents and transmits corresponding signals 58 and 59 to the regulator 57. In said regulator 57, the signal 58, corresponding to the oxygen content, is subtracted from the signal 59 , corresponding to the carbon monoxide content. The resulting signal 60 is then compared with a signal 61 corresponding to said pre-set instruction to obtain a signal 62. The signal 62 is subjected to a PID regulation law (proportional-integral-derivative) by the proportional blocks 63, integrative 64, and derivative 65, to obtain a signal 66 for regulating the motor 8 of the actuator 5 of the metering device 1.

The regulator 57 also controls the successive opening and closing of the valves 46 of the sampling devices 45, in order to take successive samples of each zone 43 and thus to regulate each metering device 1 accordingly.

Although the present invention has been described with reference to specific exemplary embodiments, it is obvious that various modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. For example, the metering device could be used for other gas mixtures than a mixture of comburent gas and combustible gas. The second nozzle could be slidably mounted, and the first fixed, so that it is the second that is moved by the actuator to approach and / or move away from each other. The oven could also be an oven with a single treatment zone, but for example a variable atmospheric composition setpoint. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

Claims (28)

Apparatus (1) for the metering of a mixture of at least two gases, such as, for example, oxidizing gas and a fuel gas, comprising: - a first nozzle (23) having a converging portion (24) and opening into an outlet (26), this first nozzle (23) communicating upstream of said convergent portion (24) with a first supply line (2) of one of said gases; a second nozzle (35) downstream of the first nozzle (23), substantially coaxial with the latter and comprising at least one convergent input portion (36) and a divergent output portion (38), one of said first or second nozzle (23,35) being slidably mounted relative to the other, the outlet (26) of the first nozzle (23) can thus be introduced into the inlet (36) of the second (35); - a chamber (34) into which a second supply line (3) opens for another of said gases, in communication with the outlet (26) of the first nozzle (23) and the inlet (36) of the second; and an actuator (5) comprising: a motor (8) with a rotary output shaft (9), a reduction gear (10) connected to said rotary shaft (9) for multiplying the rotational movement, and a conversion mechanism (11) with a rotary input connected to said reduction gear (10) and an axial output connected to the sliding nozzle for converting said downmixed rotational movement into an axial displacement movement of the sliding nozzle; said metering device (1) being characterized in that said reduction gear (10) is a worm and worm gear. The metering device (1) according to claim 1, wherein said wheel and worm gear reduction gear (10) is self-locking. 3. Dosing device (1) according to any one of claims 1 or 2, comprising at least one axial slot (29,31) in a wall of the metering device, crossed by a pin (28,30) connected to the nozzle sliding. The metering device (1) according to claim 3, wherein said pin (28,30) is connected at least to said conversion mechanism (11) to actuate the axial displacement movement of the slidably mounted nozzle. 5. Dosing device (1) according to any one of claims 3 or 4, further comprising position sensors of said spindle (28,30), such as, for example, sensors (7) end of stroke. The metering device (1) according to any one of the preceding claims, wherein said conversion mechanism (11) is a screw and nut transmission. 7. A metering device (1) according to claim 6, wherein said transmission screw and nut comprises a screw (12) non-coaxial but substantially parallel to the nozzle mounted outside the device (1). 8. Dosing device (1) according to any one of claims 6 or 7, wherein said transmission screw and nut comprises a nut (13) at least partially of synthetic material. Oven (42) comprising at least one heat treatment zone (43), an analyzer (56) for atmospheric compositions of said at least one zone (43), at least one burner (44) per zone (43), at at least one metering device (1) according to any one of the preceding claims for supplying fuel gas and combustion gas to the at least one burner (44) of each zone (43), and an electronic regulator (57) connected to said analyzer (56) and the actuator (5) of said metering device (1) for maintaining in each zone (43) an atmospheric composition substantially corresponding to a setpoint (61). 10. Oven (42) according to the preceding claim, wherein said electronic controller (57) is a PID regulator. An oven (42) according to any one of claims 9 or 10, having a plurality of said zones (43) in communication with one another. The furnace (42) of any one of claims 9 to 11, wherein said analyzer (56) comprises at least oxygen and carbon monoxide sensors. The furnace (42) of any one of claims 9 to 12, wherein said analyzer (56) is in communication with a zone sampling device (45) (43). Oven (42) according to claim 13, also comprising an extraction pump (47), and wherein each sampling device (45) comprises a three-way valve (46), a first channel of which is in communication with the corresponding zone (43), a second channel with said extraction pump (47), and a third channel with said analyzer (56). The oven (42) according to any one of claims 13 or 14, further comprising, between said at least one sampling device (45) and said analyzer (56), a cooler (50) equipped with an automatic pump (51). ), and preferably downstream of said cooler (50), a humidity sensor (52). The oven (42) according to any one of claims 12 to 14, further comprising, between said at least one sampling device (45) and said analyzer (56), a pump (53), preferably connected to a flow meter ( 55) to provide a constant flow and / or provided with a safety valve (54). 17. Oven (42) according to any one of claims 9 to 15 further comprising a device (49) for supplying a calibration gas to the analyzer (56). A furnace (42) for austenitizing or annealing bare metal wires according to any one of claims 9 to 16. 19. Oven (42) according to any one of claims 9 to 16, adapted to the treatment of glass between a melting furnace and a mold. 20. Oven (42) according to any one of claims 9 to 16, adapted to the treatment of non-ferrous metals or reagents. 21. A method of regulating a metering device (1) according to any one of claims 1 to 8 for supplying oxidizing gas and fuel gas of at least one burner (44) in at least one zone (43) d an oven (42), comprising the following steps: - analyzing the atmosphere in said at least one zone (43); comparing at least one result (60) of said analysis with a set point (61); - Controlling said motor (8) of the actuator (5) of the device according to a result (62) of said comparison for maintaining the atmospheric composition in said at least one zone (43) according to said instruction (61). 22. A control method according to claim 21, wherein said motor control follows a PID control law with respect to the result (62) of said comparison. 23. A method of regulating a metering device according to any one of claims 21 or 22, wherein in said analysis, are measured at least the relative volumetric contents of said atmosphere oxygen and carbon monoxide. 24. A method of regulating a metering device according to claim 23, wherein in said comparison the result of an operation comprising the subtraction of said carbon monoxide content at said oxygen content, or vice versa, is compared with said set point. . 25. A method of controlling a metering device according to any one of claims 21 to 24, wherein said setpoint is substantially constant. 26. Use of a furnace according to any one of claims 9 to 17 for the austenitization or annealing of metal son. 27. Use of a furnace according to any one of claims 9 to 17 for the glass treatment between a melting furnace and a mold. 28. Use of a furnace according to any one of claims 9 to 17 for the treatment of non-ferrous metals or reagents.