FR2751053A1 - Gas burner for heating tubes - Google Patents

Abstract

The burner has a metal envelope (21) with a front end which is open (25) and has two lateral surfaces (27) in which are respective seatings (26) opening at the open end an defining a transverse opening. A metal grill (30) to catch the flame defined a burner at the inside of the envelope, disposed along a cylindrical surface partially enclosing the seating and connection the two sides around the seatings. There is an ignition electrode (38) and a current source between the electrode and the mass formed by the envelope and the grill. The electrode has an active region (39) to form a spark between the seating and the grill.

Description

Gas combustion device for heating tubes
The invention relates to a gas combustion device for rapidly heating a tube or a profile, comprising:
- A metal casing having an open front end and comprising two lateral cheeks in which are provided respective notches opening at said open end and defining a transverse housing, accessible through the latter, for a tube or a section to be heated; and
- A metal flame attachment grid delimiting a burner inside the envelope, arranged substantially along a cylindrical surface partially surrounding said housing and connecting to the two cheeks around said notches.

The object of the invention is to allow easy ignition of the gas mixture passing through the grid to form a flame.

The invention relates in particular to a device of the kind defined in the introduction, and provides that it further comprises an ignition electrode and means for producing an electrical voltage between the electrode and the metallic mass formed by the envelope and the grid. , the electrode having an active spark-forming region disposed between said housing and the grid so as to be in contact with the gaseous mixture leaving the oil through the grid and to remain out of contact with any tube or profile to warm up introduced into the housing.

Various flame combustion devices are known, in particular soldering irons and torches, comprising an ignition electrode connected to a voltage source such as a piezoelectric generator. The invention makes it possible to incorporate such an electrode into a device for heating the tubes, without any risk of being damaged by contact with the tubes or profiles to be heated, and practically without changing the configuration of the existing devices.

Optional, complementary or alternative features of the invention are set out below: - The active region of the electrode is arranged at least approximately on an axis of symmetry front-rear of the envelope. .

- The electrode comprises a rod which crosses the grid substantially along said axis of symmetry, being surrounded by an insulator, said active region being folded out of said axis and resting on the insulator.

- The distance in space between the free end of the active region of the electrode and the grid is less than the distance between the electrode and the grid along the surface of the insulator.

- A connection element is attached to the rear end of the rod to electrically connect it to a supply wire.

- The connection element comprises a conductive tube whose bore is suitable for receiving the supply wire, crimped on the rod and surrounded by an insulating sheath.

- The envelope has a substantially circular gas inlet rear opening, the connection element passing through or approaching said rear opening at a distance thereof at most equal to about twice the diameter of this same opening.

- The electrode and, where appropriate, the connection element are mounted so as to slide along the axis of symmetry, an elastic return element bringing the active part of the electrode in contact with the insulator.

- The return element is a helical spring surrounding the rod and compressed between the insulator and the connection element.

- The grid is shaped so that the gas flow which passes through it circulates substantially parallel to the axis of symmetry in the vicinity of the active region of the electrode.

- The grid is folded along generatrices of said cylindrical surface in order to limit a substantially flat central region perpendicular to the axis of symmetry, crossed by it, and two wings extending respectively on either side of the median region, each between the plane of the latter and the open front end of the envelope, the median region being perforated so as to be traversed by a gas flow parallel to the axis and the wings being perforated only in zones sufficiently distant from the plane of the central region so that the gas flow which passes through them obliquely with respect to the axis passes beyond the electrode towards the front end of the envelope.

- The envelope is mounted on a bent lance comprising an injector capable of producing a jet of combustible gas oriented obliquely with respect to said axis, and said central region is full on a central strip oriented along the director of said cylindrical surface and extending opposite the injector with respect to said axis.

- The envelope can rotate 360 "around its axis relative to the lance, and said central strip extends on either side of the axis.

- The width of said strip is between a quarter and a half of the distance between the two side cheeks.

- The means for producing an electric voltage comprise a piezoelectric generator housed in an angled lance, on which the casing is mounted and comprising an injector capable of producing a jet of combustible gas oriented obliquely with respect to said axis.

- The piezoelectric generator is elongated substantially parallel to the axis of the injector and disposed in the vicinity of the latter.

- The piezoelectric generator comprises an elongated body, an actuating pusher which can slide longitudinally relative to the body at one end thereof and an electrical output wire leaving the body substantially in the direction of the pusher, the pusher and the start of the wire being turned substantially in the direction of gas injection.

- The piezoelectric generator is engaged in a through cavity of a molded lance body, closed at the front by a cap capable of sliding relative to the lance body to press said pusher, the piezoelectric generator being immobilized longitudinally between said cap and a stop protruding into the cavity.

- The lance body is made of a material that can be injected under pressure.

- The lance comprises an element which is not very conductive of heat separating the lance body from the envelope.

According to another aspect, the invention relates to a lance suitable for forming part of the device defined above and for receiving for this purpose the burner casing of this device, and also suitable for receiving other types of burners at the place of this envelope.

Advantageously, the lance according to the invention is equipped with a piezoelectric generator provided with a sheathed electrical output wire which travels internally along the wall of a tubular element suitable for channeling a gas mixture and receiving at its free end. an interchangeable burner, the wire being spaced from said wall in the vicinity of said free end so that its own free end is substantially on the axis of the tubular element and can serve as an ignition electrode for said burner.

The characteristics and advantages of the invention will be explained in more detail in the description below, with reference to the accompanying drawings, in which: - Figure 1 is a view in axial section of the burner casing of a device according to the invention, equipped with its flame attachment grid and its ignition electrode; - Figure 2 is a partial view in axial section of the device, showing the lance and the rear end of the burner casing; - Figure 3 is a sectional view of the molded body of the lance, according to line III-III of Figure 5; - Figure 4 shows the flame attachment grid before shaping; and - Figure 5 is an axial sectional view of a lance according to the invention equipped with a dart burner.

The device shown in Figures 1 to 4 is composed of a front sub-assembly illustrated in Figure 1 and a rear sub-assembly or lance illustrated in Figure 2. The lance comprises a body 1 injected under pressure in zamak comprising two tubular portions of horizontal parallel axes arranged one above the other, namely a lower portion 2 of circular profile and an upper portion 3 of square profile, interconnected by ribs 4. The circular tubular portion 2 is extended forward by another circular portion 5 of the same internal diameter, the axis of which is inclined forward and downward from the front end 6 of the portion 2. The upper wall 7 of the portion 5 extends rearward and upward to connect to the bottom wall 8 of the portion 3 at the front end thereof. An injector 9 is screwed into the rear end of the tubular portion 2, and a flange nut 10 makes it possible to fix the rigid assembly formed by the body 1 and the injector on a handle not shown. Air inlet openings 11 are formed in the side walls of the tubular portion 2, facing the outlet orifice 12 of the injector.

A cap 13 closed forwards is mounted so as to slide in the tubular portion 3 along the axis thereof. The portion 3 and the cap 13 define a housing for a piezoelectric generator comprising a body 14 elongated along the axis of the portion 3 and a pusher 15 projecting at the left end of the body 14 and which can be retracted elastically to produce an impulse of electrical tension between the metal body 14 and the metal core of a sheathed wire 16 which leaves from the underside of the body 14 in the direction of the pusher 15, that is to say towards the front of the lance and towards the left of Figure 2. The piezoelectric generator is trapped between the closed front end of the cap 13 and a pin 17 passing through the tubular portion 3 and fixed in two side holes 18 of the wall thereof. In the extreme front position of the cap 13, defined by a stop, the distance between the closed end of the cap and the pin 17 is approximately equal to the length of the piezoelectric generator with the pusher released. When the cap is pushed back, the pusher is retracted to produce an electrical impulse, and when the cap is released, it is pushed forward by the pusher to the position defined by the stop.

The front end region 5a of the tubular portion 5, of increased diameter, receives the rear end of a connection tube 19 made of a material which is not very conductive of heat such as stainless steel or not and the part of which front is fitted into the rear tubular portion 20 of the burner casing 21 shown in FIG. 1. The casing 21 has a general tubular configuration and is formed by two pieces of upper and lower sheet metal 22 and 23 mutually assembled by flanges external arranged in front and behind the plane of Figure 1. The tubular wall of the casing 21, of circular section in the rear portion 20, then gradually widens forward in the vertical direction. The parts 22 and 23 thus form respectively, at the front of the envelope, two jaws open towards the front (to the left of FIG. 1), which are bent one towards the other at the front end and are end with horizontal edges 24 which delimit a front opening 25 extending over the entire width of the envelope. The edges 24 are connected to the edges 26 of two notches formed respectively in two lateral cheeks 27 situated in front and behind the figure and each formed partly by each of the parts 22 and 23.

These notches gradually narrow from front to back to a bottom located in the region of increasing section of the envelope. The opening 25 and the notches 26 define a transverse housing for a tube 28 (or a profile) to be heated. The edge 26 of each notch has teeth 29 distributed along its edge, projecting towards the interior of the housing, on which the tube 28 can rest, and which thus limit its penetration towards the rear re.

A flame attachment grid constituted by a strip of perforated sheet metal, shown flat in FIG. 4, is folded according to a cylindrical surface having for its director a line composed of the small base and on both sides of an isosceles trapezoid, the two angles connecting these three segments being rounded. The grid 30 is housed in the envelope 21, its flat central region 31, corresponding to the small base of the trapezoid, being arranged perpendicular to the longitudinal axis of symmetry A of the envelope, and the two wings 32, each corresponding to one side of the trapezoid and with the adjacent roundness, extending from the plane of the region 31 to the front end walls of the envelope, to which they are connected slightly behind the edges 24. The lateral edges 33 of the grid s 'also support the inner faces of the cheeks 27, set back from the edges 26 of the notches, so that the grid surrounds the housing for the tube 28. The grid is supported on the front end of the envelope by to shoulders 34 of the lateral edges 33 which cooperate with recesses 35 of the cheeks 27.

The grid 30 has a central hole 36 which is axially traversed by an insulating sleeve 37 in the central bore from which a metal rod 38 serving as an ignition electrode passes. The part 39 of the electrode situated to the left of the sleeve 37 is folded back at a slightly acute angle relative to the remaining part extending axially, so that its free end 40 is located radially beyond the sleeve, at a distance of the central region 31 of the grid less than the electrical leakage distance between the electrode and this same region of the grid along the surface of the sleeve. It is thus ensured that a voltage pulse between the electrode and the grid will cause a spark between the end 40 and the grid, within the gas mixture having passed through the perforations thereof. Furthermore, the part 39 of the electrode is arranged so as to be out of reach of any tube 28 or profile introduced into the housing, taking into account the presence of the teeth 29 and the fact that this part is set back from at least 0.5 mm from the bottoms of the notches.

The rod 38 also protrudes at the rear relative to the sleeve 37 and has, in the vicinity of its rear end, a peripheral groove 41 in which is pressed locally by deformation the wall of a metal tube 42 partially threaded on the rod and protruding backwards beyond it, thus axially securing the rod and the tube by crimping. The tube 42 is covered with an insulating sheath 43 which extends rearwards beyond the rear end of the tube, and slightly beyond the rear end 45 of the cylindrical portion 20 of the envelope 21. The sheath 43 and the tube 42 are intended to guide the end of the output wire 16 of the piezoelectric generator, the core of which comes into contact, in the assembled device, with the rod 38, directly and / or by the intermediate of the tube 42. In addition, the sheath 43 acts as an insulator between the rod 38 and the tube 42 on the one hand, and the adjacent metal parts 22 and 23 on the other hand. The slight protrusion of the sheath 43 at the rear of the envelope facilitates the introduction of the wire 16 during assembly. This protrusion can be eliminated, but it is preferable that the rear end of the electrode connection element is not set back with respect to the rear end 45 of the envelope of a length greater than twice the diameter of this end. A helical spring 44, surrounding the rod 38 and compressed between the rear end of the sleeve 37 and the front end of the tube 42 and / or of the sheath 43, keeps the front part 39 of the electrode in abutment on the end front of the sleeve 37, while allowing in the event of an impact an axial displacement of the electrode and of its connection element 42, 43, relative to the sleeve and to the envelope.

It can be seen in FIG. 4 that the perforations 50 of the grid 30 are located in a central zone surrounding the hole 36 for the passage of the insulating sleeve, and in two zones adjacent to the ends of the strip, these three zones being separated by two solid zones . The gas flow passing through the perforations of the central zone circulates in the axial direction around the sleeve 37 and sweeps only the end 40 of the electrode, while the gas flows passing through the perforations of the end zones flow obliquely in the direction of the axis, in front of the electrode.

Thus, no flame strikes the insulating sleeve 37.

Due to the bent configuration of the gas path defined by the tubular portions 2 and 5, the connecting tube 19 and the casing 21 and the flared shape of the latter, the speed of the gas flow is higher in the upper half of the envelope only in its lower half. If the central region 31 of the grid had perforations at mid-width and above the central hole 36, the speed of the flow of gas passing through these perforations would be too high to allow the formation of an ignition spark. For this reason, the central region 31 is devoid of perforations on a central strip (B) whose width a, in the example shown, is approximately equal to a quarter of the total width of the grid. If the casing 22 is fixedly mounted on the lance, it is sufficient for this solid strip to extend longitudinally upwards from the hole 36. Preferably, however, the casing can rotate 360 "around the axis A to allow to surround difficult to access tubes to be heated. The grid is then symmetrical with respect to the axis A, the strip B extending on either side of the hole 36, so as to eliminate the phenomenon mentioned above in each of the two angular positions of the envelope, mutually distant from 1800, where it could manifest.

The device represented in FIG. 5 comprises a lance identical to that described in relation to FIG. 2, comprising a molded body 1 and an intermediate tube 19 and equipped with a piezoelectric generator 14, 15 with its output wire 16, and d an injector 9. A dart burner 60 is mounted at the front end of the tube 19 in place of the burner for heating the tubes described above.

As in FIG. 2, a small hole 61, adjacent to the upper wall 7 of the tubular portion 5, crosses the upper wall of the tubular portion 2 to allow the wire 16 to penetrate the tubular portion 5 along the wall 7. The wire 16 then extends in a straight line along the internal face of the tube 19 and is then deviated obliquely beyond this tube, by an angle of at least 20, so that its free end 62 is substantially on the axis of the tube 19 and of the burner 60. The end of the core of the wire 16 then serves as an ignition electrode. The configuration described is obtained by cutting the wire 16 to the desired length when assembling the lance, and by bending its end region using a tool.

Claims (21)

Claims 1. A gas combustion device for rapidly heating a tube or a profile, comprising:  a metal casing (21) having an open front end (25) and comprising two lateral cheeks (27) in which are provided respective notches (26) opening at said open end and defining a transverse housing, accessible through the latter, for a tube or a profile to be heated; and  - a metal grid (30) for attaching a flame defining a burner inside the envelope, arranged substantially along a cylindrical surface partially surrounding said housing and connecting to the two cheeks around said notches, characterized in that it further comprises an ignition electrode (38) and means (14, 15) for producing an electrical voltage between the electrode and the metallic mass formed by the envelope and the grid, the electrode having an active region (39 ) forming a spark arranged between said housing and the grid so as to be in contact with the gas mixture leaving the burner through the grid and to remain out of contact with any tube (28) or profile to be heated introduced into the housing . 2. Device according to claim 1, in which the active region of the electrode is arranged at least approximately on a front-rear axis of symmetry (A) of the envelope. 3. Device according to claim 2, in which the electrode comprises a rod which crosses the grid substantially along said axis of symmetry, being surrounded by an isolator (37), said active region being folded out of said axis and s' pressing the insulator. 4. Device according to claim 3, in which the distance in the space between the free end (40) of the active region (39) of the electrode and the grid is less than the distance between the electrode and the grid along the surface of the insulator. 5. Device according to one of claims 3 and 4, in which a connection element (42, 43) is fixed to the rear end of the rod for electrically connecting the latter to a supply wire (16 ). 6. Device according to claim 5, wherein the connection element comprises a conductive tube (42) whose bore is adapted to receive the supply wire, crimped on the rod and surrounded by an insulating sheath (43 ). 7. Device according to one of claims 5 and 6, wherein the envelope has a substantially circular gas inlet rear opening (45), the connection element passing through said rear opening or approaching at a distance of this at most equal to about twice the diameter of this same opening. 8. Device according to one of claims 3 to 7, in which the electrode and if necessary the connection element are mounted so as to slide along the axis of symmetry (A), an elastic return element (44) bringing the active part of the electrode resting on the insulator. 9. Device according to claim 8, attached to claim 5, in which the return element is a helical spring (44) surrounding the rod (38) and compressed between the insulator (37) and the connection element ( 42, 43). 10. Device according to one of claims 2 to 9, wherein the grid is shaped so that the gas flow which passes through it circulates substantially parallel to the axis of symmetry in the vicinity of the active region of the electrode. 11. Device according to claim 10, in which the grid is folded along generatrices of said cylindrical surface to delimit a median region (31) which is substantially flat and perpendicular to the axis of symmetry, crossed by it, and two wings. (32) extending respectively on either side of the central region, each between the plane of the latter and the open front end of the envelope, the central region being perforated so as to be traversed by a flow gas parallel to the axis and the wings being perforated only in zones sufficiently distant from the plane of the central region so that the gas flow which crosses them obliquely with respect to the axis passes beyond the electrode towards the front end of the envelope. 12. Device according to claim 11, in which the envelope is mounted on an angled lance (1, 19) comprising an injector (9) capable of producing a jet of combustible gas oriented obliquely with respect to said axis (A), and said middle region is full on a central strip (B) oriented along the director of said cylindrical surface and extending opposite the injector relative to said axis. 13. Device according to claim 12, wherein the envelope can rotate 360 "around its axis (A) relative to the lance, and said central strip (B) extends on either side of the axis (A). 14. Device according to one of claims 12 and 13, wherein the width (Q) of said strip is between a quarter and a half of the distance between the two side cheeks. 15. Device according to one of the preceding claims, in which the means for producing an electrical voltage comprise a piezoelectric generator (14, 15) housed in an angled lance (1, 19), on which the casing (21) is mounted and comprising an injector (9) capable of producing a jet of combustible gas oriented obliquely with respect to said axis. 16. Device according to claim 15, wherein the piezoelectric generator is elongated substantially parallel to the axis of the injector and disposed in the vicinity of the latter. 17. Device according to one of claims 15 and 16, in which the piezoelectric generator comprises an elongated body (14), an actuating pusher (15) which can slide longitudinally relative to the body at one end thereof and an electrical outlet wire (16) leaving the body substantially in the direction of the pusher, the pusher and the start of the wire being turned substantially in the direction of gas injection. 18. Device according to claim 17, in which the piezoelectric generator is engaged in a through cavity (3) of a molded lance body, closed at the front by a cap (13) suitable for sliding relative to the lance body. to push said pusher, the piezoelectric generator being immobilized longitudinally between said cap and a stop (17) projecting into the cavity. 19. Device according to claim 18, in which the lance body is made of a material which can be injected under pressure. 20. Device according to one of claims 17 to 19, wherein the lance comprises an element (19) not very conductive of heat separating the lance body (1) from the envelope (21). 21. Device according to one of claims 15 to 20, in which the lance is separable from the envelope and suitable for receiving in place of the latter different types of burners (60).