EP1941207A1 - Hot air internal ignition burner/generator - Google Patents

Abstract

The invention relates to a hot air internal ignition burner/generator comprising an injection device used for producing a high-speed fuel gas mixture stream and for injecting said stream into the burner head (2) which is tabular-shaped and comprises in-series arranged therein a pressure recovery chamber (10), an igniting chamber (11) and simple or multiple diffusion means (24) which are fixed inside the head (2), where two chambers are jointed, wherein said diffusion means (24) comprise a central orifice provided with an igniting tube which penetrates therein and axially extends inside the pressure recovery chamber (10) in such a way that it defines the ignition chamber (43) provided with igniting electrodes (42) connected to the pressure recovery chamber (10) of the burner (2) via a calibrated orifice (46).

Description

BURNER / HOT AIR GENERATOR WITH INTERNAL IGNITION

The present invention relates to a burner / generator of hot air with internal ignition.

It applies in particular, but not exclusively, to gas burners of intrinsically cold nozzle type, capable of performing external combustion of a gas mixture at high speed.

It is known that burners of this type frequently apply to the low temperature heating of plastic film, for example polyethylene film, with a view to their retraction by means of a gaseous flow coming from the combustion of a combustible gas. such as propane and air.

To satisfy this type of application, the burner must therefore be designed to produce a gas flow having a temperature of the order of 120 ° to 540 ^° C. at a predetermined distance from the burner (distance at which the plastic film to treat must be arranged).

At this distance, the temperature must be relatively homogeneous and the gas stream free of burning material, so as to avoid any possibility of burning, scorching and blistering of the film.

In order to achieve this result, it has already been proposed a burner comprising an injection device capable of producing a flow of combustible gas mixture to high speed and to inject this flow into a tabular shaped burner head successively comprising:

a pressure recovery chamber having, in the plane of symmetry of the head, a divergent shape and inside which the gaseous mixture coming from the injection device develops in a fan configuration,

an ignition chamber of substantially constant and rectangular section,

two deflectors which respectively extend the two long sides of the ignition chamber, and which converge towards each other, these two deflectors having two rectilinear front edges forming between them a passage of reduced width, and

diffusion means that may comprise a grid at the same one set of two grids, of substantially semicylindrical shape fixed inside the head at the junction of the two chambers, these diffusion means forming a convex partition, oriented parallel to said edges, in said plane of symmetry, and whose concavity is oriented towards the inside of the pressure recovery chamber.

In this burner, the diffusion means can be made from a mesh or a perforated sheet.

It turns out that, thanks to the structure described above, the burner head is not licked by the flame and thus does not undergo significant heating.

To homogenize the anterior edge of the flame and prevent undesired orientations of the burner induce heterogeneities of the flame was proposé_ _^ (request- de- patent FR 0693 8-7- θ) -d'utiliser circulars-forms for anterior edges of the ignition chamber and deflectors as well as for the diffusion grid. Furthermore, it is known that to carry out the ignition of the flame, it has already been proposed to use a spark plug mounted in a tubular housing opening into the ignition chamber through an orifice provided in a location of the wall of said chamber located at the right of the lateral zone of the grid.

However, it is found in use that this solution has a serious drawback. Indeed, the tubular housing of the candle forms a cavity generating a turbulent regime of the gas flow emitted by the perforations of the grid. As a result, a permanent self-sustaining combustion of the gas flow can be established at this cavity, causing a heating of the wall of the ignition chamber, which is contrary to the purpose.

In an attempt to overcome this drawback, it has also been proposed an ignition device involving an ignition cavity external to the ignition chamber, and communicating with it through a reduced section passage orifice provided in the wall the ignition chamber substantially to the right of the front region of the gate, the section of this orifice being provided sufficiently small to ensure that the disturbances of the gaseous mixture flow at this orifice can not generate a focus of Parasite combustion self-maintenance likely to heat the wall of the ignition chamber.

However, this solution has a disadvantage resulting from the fact that, during ignition, the generated spark causes a sudden combustion of the gaseous mixture in the ignition chamber. The gases in combustion are ejected and then ignite the flow of gaseous mixture exiting the ρerforations_centrales _ Ja grate - burner.- It -s ~ is a solution- noisy unpleasant for the operator and for people who are in his entourage. - AT -

Furthermore, it turns out that a major problem that must be solved in the design of a direct ignition device is that of the voltage and energy of the electrical pulses that should be applied to the electrodes d ignition, to effectively ignite the gas mixture flowing at high speed inside the burner. Indeed, to achieve direct ignition, the gap between the electrodes must be relatively large. This voltage and this instantaneous energy must therefore be relatively high so that it is appropriate to use, on the one hand, a sufficiently powerful generator and, on the other hand, an electrical connection between the generator and the electrodes which is particularly well isolated so as to avoid online losses or disruptions.

The object of the invention is therefore more particularly to eliminate all these disadvantages.

For this purpose, it proposes a cold nozzle gas burner of the aforesaid type in which single or multiple diffusion means comprise a central orifice into which an ignition chimney extends which extends axially inside the chamber. pressure recovery, this ignition chimney defining an ignition chamber provided with ignition electrodes in communication with the burner pressure recovery chamber through a calibrated orifice.

Thus, due to the difference in pressure existing between the calibrated orifice and the outlet orifice of the ignition coil, inside the latter is created a flow of gaseous mixture at a speed less than that of the gas flow inside the combustion chamber and a pressure, relativement_basse _^ Llusage-and-a-size orifice radially oriented prevents its external orifice is located in an area of overpressure and that the gaseous mixture present inside the ignition chamber is subjected to turbulence.

As a result, during ignition, the spark generated between the ignition electrodes causes the gaseous mixture to ignite without igniting inside the ignition chamber, and a combustion that propagates axially to the combustion chamber of the burner thus causing ignition of the burner.

It turns out that this solution has many advantages:

- The ignition chimney is constantly scanned and cooled by the gas mixture circulating in the burner pressure recovery chamber.

- Because it is not directly subjected to the action of the flame generated in the burner, this ignition chimney is not the seat of a significant rise in temperature.

- Because it is not directly in contact with the burner walls, it is not likely to cause overheating of this wall.

- Given that it is possible to generate ideal ignition conditions (flow velocity / pressure / no turbulence) inside the ignition chamber, it is possible to have in order to obtain sparks with pulses of lower energy and lower voltage than are usually required. Accordingly, the dimensions of jutilisé_etJLes_exigences generator Subject -d'-insulation-des- conductors ^"connecting the generator to the electrodes can be reduced. - Because it is confined inside the pressure recovery chamber, the ignition chimney is protected against external aggressions; it can therefore be achieved using lighter and more precise elements.

Advantageously, the tabular ignition chamber may be extended at one of its ends by a minimum cross-section chimney to prevent any backfire but nevertheless allow the propagation of the gas mixture during combustion for ignition , and the other end may be closed by a sleeve of insulating material provided with a coaxial ignition electrode. This electrode cooperates with at least one annular portion of the body made of an electrically conductive material which constitutes a second ignition electrode surrounding the first.

Furthermore, the burner previously described may be designed so as to be equipped with an extension consisting of a tabular element, possibly telescopic, which can be inserted between the nozzle of the injection device and the burner head.

However, the use of such an extension raises at least three problems, namely:

- A first problem resulting from the fact that when extinguishing the burner there remains within the assembly formed by the burner head extension and the injection manifold a relatively large volume of gaseous mixture. However, at the time of stopping the burner the flow rate of the gas mixture, in particular through the diffusion gate lowers before becoming zero. Therefore, below a certain flow velocity of the diffusion means whose perforations have been determined so as to obtain in the chamber of ignition a significant flow of gas at a relatively high level. ^" speed, no longer holds the flame. This is the reason why the combustion propagates inside the aforesaid set, generating a slight explosion. This explosion which is not devoid of any risk has the disadvantage of being noisy and, therefore, difficult to qualify in the factory or on a construction site.

- A second problem resulting from the fact that the extender is made of an electrically conductive material and is brought to the ground of the electric generator (piezoelectric). As a result, the driver who passes through the extension to connect the output of the electrical generator to the ignition electrode disposed in the ignition chamber, constitutes with said extension a capacitor whose capacitance is a function of the length of the extension and the layout of the driver inside said extension. This capacitor has the disadvantage of absorbing a large fraction of the electric charge delivered by the electric generator at the moment of ignition. The charge applied to the ignition electrode is thus weakened. - A third problem results from the fact that the gases propelled at high speed by the injection pipe do not mix homogeneously inside the extender. This heterogeneity is itself a function of the length of the extender. The use of deflectors intended to create disturbances in the gas flow to improve this homogeneity nevertheless has the disadvantage of slowing the flow, which is contrary to the desired effect in a high-speed burner.

The invention therefore also aims to solve these problems.

Thus, in order to solve the first problem, it proposes to have inside the ignition chamber, an additional grid or sieve whose mesh is smaller than that of the diffusion grid but whose section passage_totale_χ. Summe -des-section of all the meshes) - is greater à'celles ^"spreading means so as to avoid flash back inside extender without causing a noticeable slowdown of the gas flow.

Advantageously, this additional grid may be permanently disposed within the pressure recovery chamber, against or in the immediate vicinity of the diffusion means. In the case where a double diffusion grid is used, this additional grid may be arranged between the two diffusion grids.

In order to solve the second and third problems mentioned above, the invention proposes to use a rigid electrical conductor having a portion that extends obliquely between the two connecting members respectively located at the ends of the extension. This electrical conductor comes to connect:

- On the one hand, by one of its ends, on an electrically conductive washer serving as annular electric diffuser, mounted in an insulating tabular sleeve provided at the end of the extender on which engages the burner head, and

on the other hand, to a coaxial electrical connection finger, mounted on an electrically insulating support in the second end, the connector preferably forming a bend, so as to reach a region symmetrical to that of the connection to the conducting washer before return to the electrical connection finger. Of course, the distance separating the wall of the extender from the ends of the oblique portion of the electrical conductor must be greater than a determined distance so as to avoid the formation of parasitic electric arcs.

Thanks to these arrangements, the capacitance of the capacitor formed between the conductor and the extender remains in the limits of the face, owing to the performance of the ignition device previously described, and the oblique portion of the conductor. causes a progressive disruption gas flow over the entire length of the extender, and over its entire section. This disturbance, which makes it possible to obtain a homogeneous gaseous mixture, does not, however, cause a noticeable slowing down of the gaseous flow, and this, because of its progressivity along the oblique portion of the conductor.

In the case where the extender is telescopic, the electrical conductor may be made of at least two rigid elements, one of these two elements being tubular while the other consists of a cylindrical rod which engages tightly in the element tubular. These two elements have at least partially the same oblique.

The advantage of the previously described arrangement then consists in that due to the geometry of the conductor, the engagement and sliding of the two elements takes place slightly forcibly with friction between the two elements. As a result, there always exists between the two elements a contact area with contact pressure. This provides an excellent electrical connection that eliminates the risk of arcing, unlike the solution that would be to use two telescopic conductor elements oriented parallel to the axis of sliding of the two sliding portions of the extender.

Embodiments of the invention will be described below, by way of non-limiting examples, with reference to the accompanying drawings in which:

Figure 1 is a vertical sectional view of a cold nozzle type high speed short burner;

Figure 2 is a schematic section illustrating the operating principle of the burner shown in Figure 1-f- Figure 3 is a schematic perspective view of the burner head;

Figure 4 is a section on a larger scale of the burner head shown in Figure 1;

Figure 5 is a partial sectional view of an alternative embodiment of the burner of Figure 1 equipped with an extender;

Figure 6 is a partial section of the technical variants of the extension detent system and the ignition electrode connection;

Figure 7 is a schematic partial section of a telescopic extension.

In the example shown in Figures 1 to 3, the burner according to the invention comprises an injection device 1 adapted to transmit to the burner head 2, a combustible gas mixture stream.

This injection device 1 is more particularly involved:

a tubing 3 formed in two sections, namely a convergent posterior section 4 and a substantially divergent anterior section 5; an injection nozzle 6 mounted in the convergent section 4, this nozzle 6 being connected to a source of flammable gas having a pressure of the order of 1 to 4 bars, and

at least one air passage opening 7 located in the annular zone _comprise_deladiteJ3use 6 and said section-4. This device therefore forms a jet pump which drives the air coming from the opening 7 and generates in the convergent portion 4 of the tubing 3 (point I) a flow of gaseous mixture at high speed, of the order of 12 660 meters / minute. The burner head 2, of tabular form, consists of two electrically conductive metal parts, which successively delimit a pressure recovery chamber 10 which connects to the tubing and an ignition chamber 11 which opens at the same time. outdoors.

The pressure recovery chamber 10 has beyond its connection zone to the pipe 3, a flared shape delimited by two converging walls 12, 13, of increasing width and two diverging side walls 14, 15 of decreasing width. As can be seen in FIGS. 2 and 3, the front edges 16, 17 of the two convergent walls 12, 13 have coaxial circular shapes.

The ignition chamber 11 has a shape also flared. However, in this example, it is delimited by two parallel walls 18, 19 which extend the two converging walls 12, 13, and two diverging side walls 20, 21 which extend the side walls 14, 15, respectively in the same orientations. The front edges 22, 23 of the two walls 18, 19 are circular and extend coaxially with the borders 16, 17.

These two chambers 10, 11 are separated from each other by a double diffusion grid 24 which consists of two pieces of perforated sheet having the shape of a toric sector of substantially semicylindrical section, and whose large radius of curvature corresponds substantially to that of the anterior edges 16, 17 of the converging walls 12, 13. The perforated sheet, side jchambrejie.xécupération-pressure-lOj-present in-sen-center a long and narrow oblong cutout. Fixing this diffusion grid 24 inside the burner head 2 is performed in the junction zone of the chambers 10 and 11, the concavity of this gate being oriented towards the pressure recovery chamber 10.

The walls 18 and 19 of the ignition chamber 11 are extended by two circular deflectors 30, 31 which converge substantially towards one another and have two coaxial respective edges 32, 33 forming between them a passage space of width less than the width of the lateral sides 20, 21 of the ignition chamber 11.

The operating principle of this burner head is then as follows:

Inside the pressure recovery chamber 10, the speed of the gas mixture is slightly reduced while it develops in a fan configuration. At the level of the diffusion grid 24, a relatively homogeneous pressure zone is formed, due to a conversion of the kinetic energy of the gas flows.

Through the perforations of the gate 24, the fuel mixture forms a succession of jets again accelerated (point N at 2400 m / min, Figure 2).

In the middle part of the grid 24, these jets are oriented axially while in the lateral parts, they are substantially radial and abut on the walls 18, 19 and on the baffles 30, 31.

It can be seen that in the middle part of the gate 24, the gaseous flow formed by the jets undergoes a deceleration ΔVi (point O at 1600 m / nτn). This is due to the fact that at the end of the perforations of the central zone of the grid 24, it. -produit- is a relaxation-du-fuel mixture, - this ^{"relaxation ~} étanf favored by the distribution jets of the gas flow This decrease. flow rate allows the combustion to settle at a slight distance from the grate 24.

Beyond the point O, the combustion of the gaseous mixture is established and there is a slight acceleration of the gases (expansion due to combustion). However, the speed at point OO (Figure 2) remains lower than that measured at point N.

On leaving the diffusion grid 24, the speed of the gas flow is not homogeneous, which should, in principle, lead to a heterogeneity of the flame.

This disadvantage is eliminated by the use of deflectors 30, 31 which serve to deflect the fuel mixture flow zones from the side portions of the grid 24 and to make them slightly converge towards the central region of the gas flow.

At the same time, the speed of this gas flow is reduced, by entrainment effect, substantially to that of the central part of the flow. The combustion of the gaseous mixture then forms, beyond the front edges of the baffles 30, 31, a fan-shaped flame.

According to the invention, this ignition device involves a cylindrical ignition chamber 43 which extends coaxially with the head 2 of the burner inside the pressure recovery chamber 10 via a ignition chimney 44 which passes through the double perforated grid 24 at its center and opens into the ignition chamber 11 while in the other end of the ignition chamber, engages a tabular sleeve. wherein a cylindrical ignition electrode 42 having three successive steps 42 ', 42 ", 42'" corresponding to the steps of said bore is provided. The staggering 42 'of the smaller diameter electrode 42 protrudes outside the socket 41 within an ignition chamber 43.

The staging 42 '' 'of larger diameter extends outside the sleeve 41 to the level of the connection between the pipe 3 and the head 2 of the burner.

In fact, the ignition assembly 40 electrically conductive comprises: a first tubular portion 44 of small passage section, the ignition chimney, one end of which engages through the double gate 24 and the other side a second tubular portion 45 of larger internal closed section, on the side opposite the chimney, by the insulating sleeve 41 of the electrode 42.

This second tubular portion 45 delimited by the first tubular portion 44 and the sleeve of insulating material 41 equipped with the electrode 42, represents the ignition chamber 43 in which a calibrated orifice 46 opens in the tubular element 45, this orifice calibrated 46 extending radially.

The ignition assembly 40 is in electrical contact with two electrically conductive parts of the head 2 of the burner, on the one hand, via the double gate 24 and, on the other hand, by a holding piece 47 electrically conductive which extends radially in the pressure recovery chamber 10.

The head 2 of the burner fits on the end of the pipe 3 by means of an assembly to ensure both a seal and a goodconnection _electric, _entent- that- the-tubing- 3- is electrically connected to the ground of a piezoelectric generator housed in a handle P integral with said manifold 13. The actuation of the piezoelectric generator is provided by a trigger G equipping the handle P.

This assembly involves three successive coaxial grooves 48, 49, 50 axially offset, provided in the interlocking zone of the pipe 3, two O-rings 51, 52 of resilient material, respectively disposed in the first 48 and the third groove 50 and a metal blade 53 retaining resiliently deformable, whose curved end 54 is intended to engage in the central groove 49, the metal blade being secured to the burner head.

This arrangement makes it possible to obtain a rapid tight assembly despite manufacturing tolerances of the head 2 and of the pipe 3, a good electrical contact thanks to the tongue 53 and to the zones of contact between the head 2 and the pipe 3, and a seal thanks to the O-ring 52 (the O-ring 51 essentially providing a guiding and retaining role).

The piezoelectric generator is also connected to the ignition electrode 42 by means of an electrical conductor wire 63 and a connector located at the interlocking zone of the tubing 3.

In this example, this connector uses an insulating collector support 55 in the form of a floor tubular sleeve, made of insulating material, comprising a first step 56 which fits into the tubing 3 and a second step 57 of external diameter. more important which has an inner surface forming an annular groove 58.

In this annular groove, are arranged on the one hand, a washer _^ electrically conductrice.- 5-9 -connectée-au-filtered electrical conductor-63-and "serving annular electric diffuser and, on the other hand, a metal spring helicoidal 60 whose end located outwardly of the tubing is extended by a rectilinear strand 61 radial which extends diametrically.

The length of the protruding portion of the electrode 42 is determined so that, in the assembled position of the head 2 on the tubing 3, the rectilinear strand 61 of the spring 60 engages in a radial groove 62 formed in the end of the electrode 42 and remains applied in the bottom of this throat

62 in order to drive the spring 60 in rotation on the electrically conductive washer 59 during the rotation of the burner head 2, the assembly thus forming a rotating collector. (Advantageously, the end of the electrode may comprise two radial grooves at 90 ° to each other).

Thanks to these arrangements, and in particular to the compression of the spring between the rectilinear strand 61 and the washer 59, an excellent electrical contact is obtained on the one hand between the rectilinear strand 61 and the electrode 42, on the other hand between the metal washer 59 and the last grounded close coil of the spring 60.

A variant of this construction Figure 6, is to replace the aforesaid spring 60 by the spring 60 'and the washer 60 "having an axial maneuvering shape 60'" connected to its peripheral portion by one or more connecting arms. This form of maneuver engages in or around the opposite form 62 'of the electrode 74' in order to be able to drive the washer in rotation.

60 "on the spring 60 'bearing on the electrically conductive washer 59 during the rotation of the burner head 2, the assembly thus forming a rotating collector.

As previously mentioned, an advantage of the previously described solution is that. the gaseous mixture which flows into the manifold increases its pressure in the pressure recovery chamber 10. because of the presence of the double gate 24, while it falls at the exit of this double gate 24 in the combustion chamber 11.

Due to this difference in pressure and the presence of the calibrated orifice 46, there is a flow of gas mixture inside the ignition shaft 40.

When the piezoelectric generator is actuated via trigger G, the generated electrical pulse is applied to electrode 42 and ignition assembly 40 which acts as a second electrode.

This arrangement also makes it possible to rotate the head 2 of the burner with respect to the tubing 3 without causing malfunction of the burner or its ignition system.

There is thus produced between these two electrodes a spark which causes the combustion of the gaseous mixture present in the ignition chamber 43. This gas mixture in combustion moves along the chimney 44 until reaching its outlet orifice O. From that the volume of combustion gas mixture present in the combustion chamber 11 is sufficient, the gaseous mixture delivered by the orifices of the double gate 24 ignites and, consequently, produces a slight increase in pressure causing the extinction of the mixture gaseous inside the chimney.

As previously mentioned, the burner / hot air generator may comprise a tabular extender 70 interposed between the anterior end of the tubing 3 and the head 2 of the burner. In this case, in order to avoid flashbacks when the burner stops, a sieve is disposed at the same location as the grate-having-cut-oblong-in the pressure recovery chamber. or between the two grids. This GS screen comprises a central orifice through which the chimney 44 passes. In the example illustrated in Figure 5, this extension 70 consists of a rigid tube, optionally bent having, on one side, a female assembly profile PF of a type similar to that used in the burner head.

However, in this case, instead of the flexible ratchet blade 53, this female assembly profile may comprise, according to FIG. 6, a detent comprising a ball 71 retained inside a conical bore 72 by an elastic ring. 73, so that it can partially engage in the central groove 49 of the end of the tubing 3.

Furthermore, in FIG. 5, the extension 70 is provided, at this female assembly profile, with a coaxial electrical contact finger 74 mounted on a support made of electrically insulating material 75 fixed by means of the support 47 inside the extension 70 at the base of the assembly profile PF.

This electric contact finger 74 comprises in a manner analogous to that of the electrode 42, two radial radial grooves 76 intended to receive the radial rectilinear strand 61 of the spring 60.

The front end of the extension intended to receive the head 2 of the burner has a male coupling profile PM identical to that provided at the end of the pipe 3 and which will not be described again.

The electric diffusion washer 59 'equipping this male assembly profile PM is then connected to the electrical contact finger 74 via an electrically conductive connecting rod 77. This connecting rod has au _d_elà_.die _sa_çennexioji_à _the -rondelle - a edge-59- - straight -which -s ^ι extends obliquely relative to the longitudinal axis of the extender. The two ends of this section are symmetrical with respect to a midpoint located on said longitudinal axis. The end is connected to the electrical contact finger through a portion comprising a substantially radial segment and two bent ends. The benefits of this provision have been previously described and will not be exposed again.

Optionally, the extension may be bent and / or extendable telescopically.

In the latter case, it may be performed in at least two tabular sections sliding one into the other equipped with means for providing a temporary axial locking and limiting the rotational movement relative to each other.

In this case, the connecting lead wire 77 may be made in a spiral with shape memory materials, the diameter of the turns being smaller than the inside diameter of the extension. This solution makes it possible to obtain an extensible electric connection which disturbs only to a very small extent the flow of gaseous mixture circulating in the extension.

In the example illustrated in Figure 7, the extension consists of two cylindrical tubular elements 81, 82 of slightly different diameter which fit into each other telescopically.

The end of the tabular element 81 opposite to the interlocking zone comprises a connection device similar to that described with reference to FIG. 5 and which comprises a tubular sleeve 83 made of electrically insulating material, which fits partially in the element 81. This tabular sleeve 83 has a bore recess 84 against which is disposed an electrically-conductive washer-83-provided a -pate ^~ connection 86 projecting inwardly. This connection lug has a hole through which a fixing screw is screwed into a electrical socket 87 which engages an electrically conductive connection tube 88. This sleeve 87 is disposed within a sheath 89 of electrically insulating material secured to the sleeve 83 by a spacer.

Against the washer 85 is maintained applied a rotary connection member comprising an annular element 90 in contact with the washer 85 and a rectilinear element 91 provided with a central embossing which connects two diametrically opposite points of the annular element 90.

Maintaining this annular element 90 in contact with the washer 85 is provided by means of a ring 92 of electrically insulating material which fits into the tubular sleeve 83.

In the same way as the rectilinear strand 61 according to FIG. 5, the rectilinear element 91 is intended to bear against the anterior face of the electrode 42 of the burner head. Nevertheless, in this case, instead of engaging in the radial groove 62 according to FIG. 4, it engages in spaces between axially projecting studs provided on the front face of a tubular sleeve MT in which the end of the electrode 42 engages. Advantageously, the sleeve MT may comprise five studs T uniformly distributed over its circumference.

Inside the tubular element 81, the rectilinear connection tube 88 extends obliquely with respect to the longitudinal axis of the extension.

This tube 88 extends to the other end of the element 81. At this end, it is held in position in the central region of the tubular element 8-1- through a support -radial 93-made-in-a-material -electrically insulating integral with an insulating sleeve 94 partially engaged in the element 81. The end of the tubular element 82 located opposite the interlocking zone encloses a contact finger 95 similar to the finger 76 previously described, mounted on a support 96 made of electrically insulating material, and provided with two radial grooves. cross intended to receive the straight radial strand 61 of the spring 60 equipping the end of the pipe 3. At the opposite radial grooves, the contact finger 95 comprises a cylindrical cavity in which engages an electrically electric rod 97. This rod 97 comprises, at the outlet of the cavity, a first elbow 98 and then a substantially radial portion 99 which extends to reach a region situated at a determined distance D from the wall of the tubular element 82.

The rod 97 then has a second bend 100 which extends obliquely with respect to the longitudinal axis of the extension, to be introduced into the electrical connection tube 88 (the oblicity of the tube 88 being substantially equal to the obliquity of the rod 97).

Thus, when a relative displacement of the two tabular elements 81, 82 causes a sliding of the rod 97 inside the tube 88. In parallel, it causes an elastic flexion of the rod 97 in its part located at the outside the tube 88. As a result, there is permanently obtained an electrical contact with contact pressure, between the rod 97 and the tube 88 irrespective of the relative position of the tabular elements 81, 82. Similarly, any game that can be eliminated is eliminated. be the seat of electric arcs during the ignition process. As previously mentioned, this solution also provides the advantage of causing progressive homogenization of the gas flow without causing significant slowdown of this flow.

Another advantage of this solution is that the tabular elements 81 and 82 can be rotated relative to each other without causing any disturbance in the electrical connection.

Claims

claims 1. Burner / internal-type hot air generator of the type comprising an injection device capable of producing a flow of combustible gas mixture at high speed and of injecting this flow into a burner head (2), of tabular shape comprising successively a pressure recovery chamber (10), an ignition chamber (11) and single or multiple diffusion means (24) fixed inside the head (2) at the junction of the two chambers, characterized in that diffusion means (24) comprise a central orifice into which an ignition chimney (44) which extends axially into the interior of the pressure recovery chamber (10) opens, this chimney of ignition (44) defining an ignition chamber (43) provided with ignition electrodes (42) in communication with the burner pressure recovery chamber (10) through a calibrated orifice (46). 2. Burner according to claim 1, characterized in that the aforesaid calibrated orifice (46) is oriented radially relative to the longitudinal axis of the head (2) of the burner. 3. Burner according to one of claims 1 and 2, characterized in that it comprises an ignition assembly (40) having a tabular ignition chamber (43) bounded on one side by the ignition chimney of small passage section (44) and closed on the opposite side to its opening in the ignition chamber by a sleeve of insulating material (41) provided with a first coaxial ignition electrode (42). 4. Burner according to claim 3, _caractéris.é_en_ce-than-said-electrode-(42) -coΘpère-with-at least-a ^{~ ^} portiσn annular body made of an electrically conductive material which constitutes a second ignition electrode surrounding the first (42). 5. Burner according to claim 2, characterized in that the aforesaid calibrated orifice (46) is located in the ignition chamber (43). 6. Burner according to one of the preceding claims, characterized in that the ignition chimney (40) is made of electrically conductive metal materials. Burner according to one of the preceding claims, characterized in that the said electrodes are connected to an electric pulse generator housed in the burner handle. 8. Burner according to one of the preceding claims, characterized in that the said diffusion means comprise at least one diffusion gate. 9. Burner according to claim 8, characterized in that the burner head comprises an additional grid or sieve whose mesh is smaller than that of the diffusion grid but whose total passage section is greater than that of said diffusion grid . 10. Burner according to claim 9, characterized in that the said additional grid or sieve is permanently disposed within the pressure recovery chamber. 11. Burner according to claim 9, characterized in that the diffusion means comprise two grids diffusiθΛ_et__erL ce_.que-the-additional-gate- is arranged entπe ^{~ ~} two diffusion grids. 12. Burner according to one of the preceding claims, characterized in that the burner head engages the end of the tubing of the injection device by means of an assembly including sealing means and means of electrical connection allowing a rotation of the burner head relative to the tubing. 13. Burner according to claim 12, characterized in that the aforesaid assembly involves three successive coaxial grooves (48, 49, 50) axially offset, provided in the interlocking zone of the pipe (3), two O-rings (51 , 52) of resilient material, respectively disposed in the first (48) and third (50) grooves and a resiliently deformable retaining metal blade (53) whose curved end (54) is intended to engage in the central groove (49), this metal blade being secured to the burner head. 14. Burner according to one of claims 7 to 13, characterized in that the piezoelectric generator is connected to the ignition electrode (42) by means of an electrical conductor wire (63) and a collector located at the zone interlocking of the tubing (3). 15. Burner according to claim 14, characterized in that the aforesaid collector comprises an insulating collector support (55) in the form of a tabular sleeve which fits into or on said tubing (3). 16. Burner according to claim 15, characterized in that the insulating collector support of said collector is provided with an annular groove housing a spiral spring (60) resting on a washer. to the above-mentioned conductive wire and one end of the spring (60) is extended by a radial straight strand and, secondly, at least one radial groove (62) formed in the end posterior of the first electrode and arranged so that at the end of assembly of the burner head (2) on the pipe (3), the straight strand (61) bears in the bottom of the groove (62). ). 17. Burner according to claim 15, characterized in that the insulating collector support of the aforesaid collector is provided with an annular groove housing a spiral spring (60 ') resting on one side on a connected electrically conductive washer (59). to the aforesaid wire and whose other side is supported on a washer (60 ") having an axial maneuvering shape (60 '") connected to its peripheral portion by one or more connecting arms and on the other hand a shape opposed operation (62 ') performed in the rear end of the first electrode and disposed so that at the end of assembly of the burner head (2) on the pipe (3) this form maneuver s' engages in or around the opposite shape (60 '") of the washer (60"). 18. Burner according to one of the preceding claims, characterized in that it comprises a tabular extender (70) interposed between the anterior end of the tubing (3) and the head (2) of the burner. 19. Burner according to claim 18, characterized in that it comprises an electrical connection passing inside the extension, this electrical connection consisting of a connecting rod having a rectilinear section which extends obliquely with respect to the axis. longitudinal extension. Burner according to claim 18, characterized in that the extender consists of a rigid tube; optionally bent, having on one side a female assembly profile adapted to connect to the male assembly profile of the end of the tubing (3) and, on the other side, a male joining profile (PM) identical to that of the tubing, in that at the base of the female joining profile, the extension comprises a finger of coaxial electrical contact (74) mounted on a support of electrically insulating material (75), said electrical contact finger comprising at least one radial groove 76 intended to receive the radial straight strand (61) of the spring (60) of the assembly profile male of the tubing (3), and in that the electric diffusion washer (59 ') equipping this male assembly profile (PM) is then connected to the electrical contact finger (74) via a wire optionally flexible connecting conductor (77) sheathed in an insulating coating. 21. Burner according to claim 20, characterized in that the electrical contact finger of the extender comprises a form of maneuver which engages in or around the opposite form (60 '") of the washer (60"). 22. Burner according to one of claims 20 and 21, characterized in that the female assembly profile of the extender is similar to that of the burner head with the difference that the flexible tongue is replaced by a ball catch. 23. Burner according to one of claims 18 to 22, characterized in that the extender is extensible telescopically and in that, in this case, the electrical connection comprises a conductive connecting wire made in a spiral using materials to shape memory. 24. Burner according to one of claims 18 to 22, characterized in that the extension is telescopically expandable, and in that the -leetric connection is-made-at least two oblique rigid elements ^* relative to the axis longitudinal extension, one of these two elements being tabular while the other consists of a cylindrical rod which engages tightly in the tabular element. 25. Burner according to claim 24, characterized in that the two conductor elements have at least partially the same obliquity. 26. Burner according to one of claims 18 to 25, characterized in that the extension comprises two cylindrical tabular elements (81, 82) which fit into each other telescopically, the end of one of these tabular elements comprising, opposite the interlocking zone, a tubular sleeve (83) of electrically insulating material, which partially fits into the element (81), this tabular sleeve (83) presenting a recess of bore (84) against which is disposed an electrically conductive washer (85) provided with an inwardly projecting connecting lug (86), connected to said electrical connection, in that, against the washer (85) a rotational connecting member is maintained which comprises an annular element (90) in contact with the washer (85) and a rectilinear element (91) provided with a central embossing which connects two diametrically opposite points of the annular element (90). , maintaining this the annular element (90) in contact with the washer (85) being provided by means of a ring (92) of electrically insulating material which fits into the tabular sleeve (83), and in that the straight strand (61) the rectilinear element (91), which is intended to abut on the anterior face of the aforesaid electrode (42) engages in spaces between axially projecting pins, provided on the front face of a sleeve tubular (MT) in which engages the end of the electrode (42).