EP0452379B1 - Linear gas-burner with adjustable width - Google Patents

Abstract

PCT No. PCT/FR89/00004 Sec. 371 Date Jul. 2, 1991 Sec. 102(e) Date Jul. 2, 1991 PCT Filed Jan. 4, 1990 PCT Pub. No. WO90/07680 PCT Pub. Date Jul. 12, 1990.This burner comprises a gas distributor (20) with a row of gas injectors (5a to 5e), the tube being axially inside an air distributor tube. Each gas injector extends through the wall of the air distributor tube via a coaxial air outlet aperture. The gas distributor tube includes two sealing bodies (36, 37) sliding symmetrically on either side of a central gas inlet aperture (21). Each of these bodies is provided with an eccentric longitudinal threaded bore (38, 39) engaging a threaded section of a rotating control rod (41). The two sections (48, 49) are threaded in opposite directions to the thread of the sealing bodies (36, 37), which enables them to move these two sealing bodies simultaneously in order to gradually interrupt or restore the supply of gas to the injectors (5a to 5e) situated at the end of the row without interrupting the supply to the air injectors.

Description

The present invention relates to a linear gas and blown air burner, comprising an air distributor tube connected to a pressurized air supply, a gas distributor tube mounted inside the air distributor tube and provided with a gas inlet connected to a pressurized gas supply, and at least one longitudinal row of gas injectors, these injectors extending substantially radially from the gas distributor tube through air injectors mounted on orifices air outlet formed in the wall of the air distributor tube, each gas injector being mounted on a gas outlet orifice formed in the wall of the gas distributor tube.

Such a linear gas burner, described in European patent N ° 0190091, has great advantages from the point of view of safety, since the mixing of the gas with the blown air takes place only at the entrance to the combustion zone. , and from the point of view of operating convenience since it has a very high ratio between its maximum power and its minimum power. This is why it is very widely used, especially in the food industry and in the textile industry. This is the case in particular in textile finishing machines, especially the drying and heat setting reams, where it allows both an optimal distribution of heat over the entire surface of the product to be treated and a power modulation which will up to 1:50 and which allows, in applications as different as drying fabrics or heat setting dyes, work at very precise temperatures whatever the heat requirement. With this in mind, we are starting to use such linear gas burners in place of steam, electricity or thermofluid heating, to internally heat dryer drums formed by a rotating metal casing over which passes a strip of a product to be dried such as cloth, paper, etc. On the one hand, the gas currently represents a cheap energy, usable with a very high output and on the other hand, it allows obtaining higher temperatures than a steam heating, which is necessary in certain treatments thermal. In addition, more precise and better distributed temperatures are obtained, in particular with respect to thermofluid or electric heating. Finally, a gas burner represents a heating installation capable of being operated independently, without being linked to other installations and in particular to a boiler room. Furthermore, compared to other types of linear gas burners such as premix burners, the use of a burner of the type indicated above is particularly advantageous thanks to its wide possibility of power modulation, allowing a very precise setting.

However, there is a need to be able to adjust the width of the heated zone in a fairly fine manner. For example, in a fabric drying drum, tests have shown that the regularity of drying is closely related to the active width of the gas burner. If the fabric is wider than the burner, its edges are insufficiently dried. If the burner has an active width greater than the width of the fabric, the latter is excessively dried near its edges. Indeed, the end zones of the drum, which are not covered by the fabric but are nevertheless heated by the burner, can reach an excessive temperature of up to about 400 ° C. which is detrimental to both the drum and the drum. 'to the fabric. If gas and combustion air premix burners are used, it is not too difficult to make a mechanism which reduces the active length of the burner, by progressively closing gas outlet orifices. The publication GB-A-204 756 shows a linear premixed gas burner having a distributor tube supplied at mid-length and closed by two pistons mounted on an axial shaft threaded in two opposite directions. However, this type of premix burner belongs to a technology fundamentally different from that of pure gas burners and has other disadvantages mentioned above. In a pure gas and supply air burner of this type, one solution could consist in dividing the burner into several linear or point burners, with external valves on the corresponding gas supplies. However, such a solution is complicated, bulky and expensive, and it allows only a relatively coarse adjustment step.

The present invention therefore aims to provide a linear gas burner of the type indicated in the preamble, equipped with a device for precisely adjusting the active width of the flame, keeping it engaged or not, in a way individual, at least the injectors located near one end of the row.

To this end, the burner according to the invention comprises a gas distributor tube closed internally by at least one sliding shutter member arranged to block the supply of gas to a section of this tube comprising one or more gas injectors, said shutter member being coupled to a control bar disposed longitudinally in this tube and connected to control means located outside this tube, and all the air injectors of said row continue to be supplied with air when the gas supply to one or more gas injectors is blocked by said shutter member.

In a preferred embodiment, the control bar is rotatable about its axis and comprises at least one threaded section which is engaged in a corresponding threaded bore of the shutter member, and the shutter member is provided with means preventing it from rotating in the gas distributor tube. The control bar can be rotatably mounted in two elements closing the ends of the gas distributor tube, the bar passing through at least one of the elements to be connected to the control means.

According to the essential characteristic of the burner of the invention, the gas distributor tube has a circular cross section, as does the closure member, and to prevent the closure member from rotating in the tube, the bar control and the threaded bore of this member are arranged along an axis which is offset from the axis of the tube.

This solution represents an undeniable technical progress, in particular compared to the device disclosed by the British document, because it allows to obtain a much better seal, since the sliding surfaces are cylindrical, and a clearly simplified construction insofar as one is freed from any form of guide with key and groove or equivalent, mechanically more complex and hydraulically less sealed.

In a particularly advantageous embodiment, the gas distributor tube is equipped with two sliding shutter members and a lateral gas inlet located between these two members. Preferably, the control bar comprises two elements threaded in opposite directions and engaged respectively in the two shutter members, so as to slide these two members simultaneously in opposite directions. The control bar can be connected to the control means by means of a removable coupling.

• La figure 1 est une vue schématique en élévation latérale, partiellement coupée, d'une forme de réalisation d'un brûleur à gaz selon l'invention,
• La figure 2 est une vue schématique en coupe transversale de ce brûleur, suivant la ligne II-II de la figure 1,
• La figure 3 est une vue en coupe longitudinale, suivant la ligne III-III de la figure 4, du tube distributeur de gaz de ce brûleur et du mécanisme de réglage qu'il contient,
• La figure 4 est une vue en coupe transversale suivant la ligne IV-IV de la figure 3, et
• La figure 5 est une vue analogue à la figure 4 et représente une autre forme de réalisation, toutefois non couverte par l'étendue de la protection, telle que définie par la revendication 1.

The present invention will be better understood with the aid of the following description of an exemplary embodiment, with reference to the appended drawings in which:

• FIG. 1 is a diagrammatic side elevation view, partially cut away, of an embodiment of a gas burner according to the invention,
• FIG. 2 is a diagrammatic view in cross section of this burner, along line II-II of FIG. 1,
• FIG. 3 is a view in longitudinal section, on line III-III of FIG. 4, of the gas distributor tube of this burner and of the adjustment mechanism which it contains,
• FIG. 4 is a cross-sectional view along the line IV-IV of FIG. 3, and
• Figure 5 is a view similar to Figure 4 and shows another embodiment, however not covered by the scope of protection, as defined by claim 1.

With reference to the figures, the linear burner shown comprises an external air distributor tube 1, a gas distributor tube 2 mounted inside the tube 1 in an adjustable position by means of a pair of threaded rods 3 screwed into the wall of the tube 2 and provided with locking nuts 4, and a row of gas injectors 5 fixed to the tube 2 perpendicular thereto and extending outwards, each through an air injector 6 formed by a tubular opening fixed in an orifice 7 of the tube 1. Each air injector contains a swirl ring 8, favoring the mixing of the gas and the combustion air at the outlet of the gas injector 5. This type of injector is fine known and it is described in more detail in EP-A-0 190 091. In the present case, each gas injector 5 is provided with a threaded base 9 which is screwed into a threaded bore 10 of the gas distributor tube 2 .

The injectors 5 and 6 are arranged in a row and all open into a combustion zone 11 defined by a flame guide 12 made of refractory steel, which is fixed externally to the tube 1 by bolting in slides (not shown), themselves same bolted to the tube 1. The flame guide 12 carries an electric igniter 16 and a flame control device 17, for example by detection of ultraviolet radiation. The arrangements mentioned above are well known in the field of gas and supply air burners.

In this preferred embodiment, the gas distributor tube 2 is a straight cylindrical tube, having a longitudinal axis 20 disposed approximately, but not necessarily, in the center of the tube 1. In the middle of its length, the tube 2 is provided with '' a side gas inlet nozzle 21 connected to a supply pipe 22 which passes through the wall of the tube 1 and which supplies the burner with gas coming, as indicated by arrow G, from a control valve not shown . This valve allows to regulate the gas flow, therefore the power of the burner. The gas may for example be natural gas, liquefied petroleum gas or a manufactured gas such as town or blast furnace gas. Through the interior of the tube 2, it reaches the various injectors 5 mounted in the orifices 10.

One end 24 of the air distributor tube 1 is connected to an air supply pipe 25, by a flange assembly 26 equipped with a diaphragm 26a controlling the air flow, which is blown at low pressure and arrives as indicated by arrow A, then passes around the gas distributor tube 2 to reach the air injectors 6 which mix it with the gas at the entrance to the combustion zone 11. The other end 27 of the tube 1 is closed by a cover 28 fixed to a flange 29 of the tube and traversed by a control shaft 30 provided with a manual flywheel 31 or with an automatic control.

The gas distributor tube 2 is shown in more detail in FIGS. 3 and 4. It is a straight cylindrical steel tube, supported by the threaded rods 3 and carrying the gas injectors 5. For simplicity, there is n 'has shown that five gas injectors 5a to 5e. Each end of the tube 2 is closed by a plate 32, 33 fixed by means of a threaded cap 34, 35 screwed externally to the tube 2.

Two closure nuts 36, 37 are slidably mounted in the inner bore of the tube 2 and each of them closes this bore in a sealed manner between the corresponding end of the tube and the gas inlet nozzle 21. Each of these nuts can be formed for example by a cylindrical piece of bronze pierced with an eccentric longitudinal bore provided with a thread 38, 39 and centered on an axis 40 which is offset by a distance E with respect to l 'axis 20 of the tube 2 and the outer surface of the nut. In this example, this offset E is lateral, but it could be provided in another direction. A rotary bar 41, also centered on the axis 40, extends longitudinally in the tube 2 and is carried by gland bearings 42, 43 mounted in the plates 32 and 33. One end 44 of the bar 41 passes through the cap 35 and is connected to the control shaft 30 by means of a suitable coupling 45 (FIG. 1), for example a fork coupling. Inside the tube 2, the rotary bar 41 is subdivided into two symmetrical elements 48 and 49 which are made integral in rotation by a coupling sleeve 50 and elastic pins 51, approximately in the middle of the length of the tube 2. In this zone, each element 48, 49 has a cylindrical section 52, 53 rotatably supported by a respective spacer 54, 55 fixed in the tube 2 by screws 56. On the side of the middle of the tube, the element 48, 49 is retained longitudinally by an elastic ring of the "circlip" type 57. On the other side of the spacer, it is of larger diameter and is provided with a thread 58, 59 engaged in the thread 38, 39 of the corresponding nut 36, 37. The threads 39 and 59 are in the normal direction, while the threads 38 and 58 are in the opposite direction. Each spacer 54, 55 is pierced with several holes 60, 61 for the passage of gas along the tube 2.

Thus, when one acts on the control wheel 31 so as to rotate the bar 41 in the direction of the arrow F, therefore in an anticlockwise direction, the two nuts 36 and 37 cannot turn thanks to the fact that the bar 41 is held by its bearings in an eccentric position, and slides in the tube while approaching symmetrically one from the other, while they move away if the bar 41 is turned in the opposite. Approaching, the nuts 36 and 37 will close the orifices 10 in which are mounted the two injectors 5a and 5e located at the end of the row. The linear flame of the burner will be symmetrically shortened by a small distance at its two ends, each time that the nuts 36, 37 block the supply of an additional pair of injectors 5. Likewise, the flame will widen if the 'the handwheel 31 and the bar 41 are turned in the opposite direction. Of course, provision can be made to adjust the gas supply flow at the same time. This adjustment can be done automatically using a pressure sensor on the supply line 22. In another embodiment, it can be controlled by a motorized control of the flame width adjustment mechanism, actuating the rotary bar 41. During this time, the air continues to be supplied to the combustion zone 11 by all the injectors 6, even where the injectors 5 no longer receive gas. In a drying drum as mentioned above, this has the advantage of helping to cool the end regions of the drum.

The eccentric arrangement of the bar 41 is not essential, as shown in FIG. 5. In this variant, the nuts 36, 37 are replaced by nuts 66, 67 having a threaded bore centered on the axis 20 of the tube 2 In order to be prevented from turning, each nut is provided with a lateral groove 68 which slides on a corresponding longitudinal key 69, fixed in the tube 2 by screws 70 and extending over the entire length of the stroke of the 'nut. This arrangement makes it possible to dispense with the spacers 54, 55 of the previous example and to use a bar 41 in one piece. However, the eccentric arrangement has the advantage of facilitating sealing and manufacturing. In another variant, each nut 36, 37 or 66, 67 could also be designed in two elements, one of which provides sealing and the other serves as the nut proper on the thread of the bar 41.

It should also be noted that the shutter members constituted by the nuts 36, 37 could be replaced by members controlled in a different manner, for example by means of sliding rods controlled from the outside of the burner by a linear actuator.

Claims (5)

1. Linear and forced air gas burner comprising an air distributing tube (1) connected to an air supply under pressure (A), a gas distributing tube (2) mounted inside the air distributing tube and provided with a gas inlet (21) connected to a gas supply under pressure (G), and at least one longitudinal row of gas injectors (5) extending substantially radially from the gas distributing tube, through air injectors (6) mounted on the air outlet openings provided in the wall of the air distributing tube, each gas injector being mounted on a gas outlet opening (10) provided in the wall of the gas distributing tube, the gas distributing tube (2) being blocked internally by at least one sliding blocking element (36, 37, 66, 67) arranged to block the gas supply from a section of this tube comprising one or several gas injectors (5), said blocking element being coupled with a control rod (41) disposed longitudinally in the tube and connected to control means (30, 31) located outside this tube, said rod being rotary about its axis (40) and comprising at least one threaded section (58, 59) which is engaged in a threaded bore (38, 39) corresponding to the blocking element (36, 37, 66, 67) which is provided with means (68, 69) preventing it from turning in the gas distributing tube, all the air injectors (6) of said row continuing to be supplied with air when the supply of gas of one or several gas injectors (5) is blocked by said blocking element, a burner in which the gas distributing tube (2) has a transverse, circular section like the blocking element (36, 37) and in that, to prevent the blocking element from turning in the tube, the control rod (41) and the threaded bore (38, 39) are disposed along an axis (40) which is offset in relation to the axis (20) of the tube.
2. Burner according to claim 1, characterized in that the control rod (41) is mounted such that it is rotary within two elements (32, 33) which close the ends of the gas distributing tube (2), this rod crossing at least one of these elements to connect with the control means (30, 31).
3. Burner according to one of claims 1 and 2, characterized in that the gas distributing tube (2) is fitted with two sliding blocking elements (36, 37, 66, 67) and a lateral gas inlet (21) located between these two elements.
4. Burner according to one of the preceding claims, characterized in that the control rod (41) comprises two threaded elements (48, 49) in opposite directions and engaged respectively in the two blocking elements (36, 37) in a manner such that they cause these two elements to slide simultaneously in opposite directions.
5. Burner according to one of the preceding claims, characterized in that the control rod (41) is connected to control means (30, 31) by the intermediary of a disconnectable coupling (45).

Images