An oxycutting system and a pilot flame device for said system |
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申请号 | EP12193970.6 | 申请日 | 2012-11-23 | 公开(公告)号 | EP2599573B1 | 公开(公告)日 | 2015-03-04 |
申请人 | A.L.B.A. S.r.l.; | 发明人 | D'Ottavi, Riccardo; Pirozzi, Franco; | ||||
摘要 | |||||||
权利要求 | |||||||
说明书全文 | The present invention relates to an oxycutting system comprising an oxycutting device and a device for generating a pilot flame for igniting said oxycutting device, in accordance with the characterising part of the independent claims. In the present context, an oxycutting device means the usual oxycutting torches used for some considerable time in oxycutting machines, for example in the machine manufactured and marketed by the same applicant. Known oxycutting devices are usually used for cutting billets, blooms, thick slabs, and beam blanks, and are preferably mounted on carriages provided for example in continuous casting plants. Known oxycutting systems also comprise a device for generating a pilot flame arranged to "ignite" the oxygen mixture of the oxycutting device when this latter is to be used. Although known oxycutting systems, and in particular pilot flame devices, have been in use for several decades they present numerous drawbacks which have not yet been resolved. A first technical problem of known pilot flame devices is linked to the fact that the flame can become extinguished, for example if the flame comes into contact with possible water sprays and/or because of air flows within the cutting zone, in particular in continuous casting plants. If the pilot flame is extinguished it is impossible to ignite the oxycutting device when this is to be used, and if the system is used in continuous casting it may be necessary to halt a casting line, with evident serious consequences. The flame restart in the pilot flame device is also dangerous and uncomfortable, in particular in continuous casting plants, as it requires the intervention of specialized personnel who have to approach the device in order to then manually reignite said flame. For igniting an oxycutting device, Finally, the sensor of the prior patent under examination is not reliable, is not able to sense the presence of the pilot flame during reignition of the oxycutting torch, and cannot be used in continuous casting plants, i.e. when the products to be cut are at high temperature, for example a temperature between about 700°C and 1000°C. All the devices of the aforestated prior patents can be used only in cutting plants for products at ambient temperature, such as cold sheet metal cutting plants, but cannot be used in plants for cutting products at high temperature (for example temperatures between 700°C and 1000°C), such as continuous casting product temperatures. Flame sensing devices of the prior art cannot function at continuous casting working temperatures (i.e. at temperatures in which the product to be cut is at a temperature between 700°C and 1000°C). An object of the present invention is to provide an oxycutting system comprising an oxycutting device and a device arranged to generate a pilot flame for igniting said oxycutting device which overcomes the aforesaid drawbacks and which in particular is able to reliably ensure the continuous presence of the flame in pilot flame devices, and which enables a system and a device to be produced which are of a smaller bulk and with a lesser number of components than corresponding systems and devices of the known art.A further object of the present invention is to provide an oxycutting system comprising an oxycutting device and a device arranged to generate a pilot flame for igniting said oxycutting device which can be used in a continuous casting plant, i.e. in a plant for cutting manufactured products having a high temperature (greater than 600°C).These and other objects which will be apparent to the expert of the art are attained by a system and device in accordance with the characterising part of the main claim.The present invention will be more apparent from the accompanying drawings, which are provided by way of non-limiting example and in which: The The elongate element 7 comprises at a first end 8 a nozzle 9 ( Advantageously, means 12 are also provided at the nozzle 9 for automatically igniting the mixture to generate the pilot flame 50. More particularly, the elongate tubular element 7 presents at its upper end a three-way element 14 rigidly connected to said end, for example by a threaded connection, and presenting: a first 15 and a second 17 tubular element for sealedly connecting to said first end 13 a first conduit 16 and a second conduit 18, respectively, for feeding a combustible gas, for example methane gas and air, preferably forced air, into the internal cavity 7A of the tubular element 2, a third tubular element 19 housing certain components, described in detail hereinafter, of the ignition means 12 and sensing means 11, and a connection member 20 for an electric cable 26. The tubular element 2 and the three-way tubular element 14 are made of conventional materials and with the usual finishes for components able to withstand the serious conditions present in a continuous casting plant. Preferably the tubular elements 15 and 17 comprise usual manual valves 22, 23 for regulating the flow rate of the combustible gas and forced air entering the tubular element 7. The sensing means 11 and ignition means 12 comprise an electrically conductive element 24 passing through and housed within the cavity 7A of the tubular element 7, and insulated from the inner wall 7B ( Advantageously the electrically conductive element 24 comprises a metal rod having a diameter between 1 and 5 mm and preferably 3 mm, while the insulating elements 55 comprise a plurality of tubes of an electrically insulating material, for example ceramic, to be drawn about the rod 24, as shown in Preferably the electrically conductive element 24 comprises a lower portion 24A and an upper portion 24B ( The ignition member 25 is for example of the type marketed under the brand name Kromschroder of the company Elster and transmits to the lower end 24C ( The pilot flame device 2 comprises lowerly the terminal element 27, presenting means 28 for removably associating it with the lower end ( More particularly, the box element 32 comprises a lateral wall 32A, for example of tubular shape, partially closed lowerly by a base wall 32B preferably inclined to the axis L of said wall 32A by an angle A between 1° and 90° and preferably about 60°, such as to optimally direct the flame 50 towards the nozzle 4 of the oxycutting device. The aperture 29 advantageously has a height H1 of between about 1/2 and 1/8 of the height H of the wall 32A and preferably of about 1/6, and extends through an arc of between about 45° and 180° of the circumference of said part, and preferably about 90°. In this manner, as explained hereinafter, the flame is initially enclosed within a chamber of adequate dimensions, sufficient to generate on the terminal portion 24C of the rod a flame sufficient and able to generate by ionization a current within the rod itself. Advantageously the height H2 of the chamber before the aperture 29 is between 50 mm and 70 mm and is preferably about 60 mm. The lateral wall 32A is preferably removably connected, for example by a screw connection 33, to a clamping spacer ring 34, and to a sleeve element 35 coaxial to the wall 32A and secured, for example by a thread, to an annular portion 30A of the intermediate piece 30. Advantageously, the sleeve element 35 extends below the mouth 9A of the nozzle 9 by a length M1 between 5 mm and 20 mm and preferably 10 mm such as to ensure, as explained hereinafter, an optimal ignition of the pilot flame. By virtue of the removable connection of the box element 32 to the intermediate piece, on the one hand said element can be positioned such that its aperture 29 is correctly positioned relative to the nozzle 4 of the oxycutting device, and on the other hand when the pilot flame device is inactive said element can be removed to clean it and/or check the state of the nozzle and/or of the terminal portion 24C of the rod 24. The intermediate piece 30 comprises a tubular upper part 30B, the annular central part 30A, and a lower part 30C presenting the nozzle 9. The upper part 30B and the lower part 30C preferably have a diameter which decreases downwards and is less than the internal diameter of the tubular element 7. The upper part 30B upperly presents a thread 30D for connection to the part 31 connecting the terminal element 27 to a lower portion of the tubular element 7. The connection part 31 comprises a tubular element 31A dimensioned such as to be mounted gas-tight about a lower portion of the tubular element 7. The connection part 31 comprises the connection means 28 which are advantageously of the type comprising a screw 28A, and enabling the distance D1 between the lower edge 9 of the tubular element 7 and the mouth 9A of the nozzle 9 to be varied, consequently varying the length T1 of that portion of the rod 24 which projects from said mouth. Advantageously, in its terminal part the rod 24 is maintained coaxial to the tubular element 7 by a first bush 32 in contact with the outer wall of a lower terminal portion 55A of the insulating ceramic element 55 and also protected by a further lower bush 53. According to the invention, the terminal part 24A of the rod 24 projects by a section T1 from the mouth 9A of the nozzle 9 for exit of the combustible mixture for the flame, the section T1 having a length between 8 mm and 23 mm and preferably about 13 mm. In this respect it has been verified experimentally that, as will be further explained hereinafter, for correct sensing of the flame presence, it is advantageous if a terminal portion of the rod 24 is stably and constantly surrounded by the pilot flame. Again according to the invention, to ensure reliable ignition of the combustible mixture the lower free end 24C of the rod 24 should advantageously be at a predetermined distance D2 from the lower edge 35A of the sleeve element 35, this distance D2 being preferably between 1 and 5 mm and preferably equal to about 3 mm. Advantageously to optimize the dimensioning and bulk of the pilot flame device, the tubular element 7, the rod 24 and the nozzle 9 are all coaxial to each other and to the longitudinal axis L of the tubular element 7, with the rod 24 being provided in the interior of the tubular element 7 and passing through the nozzle 9. According to the invention, when the system is operative, the pilot flame device must constantly present a pilot flame to be thus always ready to ignite the oxycutting device, and the presence of this flame must be constantly monitored. For this purpose, when the pilot flame is present the control unit 40 receives an electrical signal generated by the ionization effect of the flame 50 striking and surrounding the terminal part of the rod 24. This ionization effect generates in the rod 24 a current of low intensity, for example of the order of 1-30 µA, preferably between 10/12 µA for optimal reading, which is fed via the rod 24, the spark-plug 25 and the cable 26 to an inlet of the control unit 1. The control unit verifies, preferably continuously, the presence of the electrical signal originating from the rod 24, the presence/absence of which indicates the presence/absence of the flame. It should be noted that to achieve an adequate intensity of the current signal sensed by 24 the ratio of the gas to air producing the pilot flame 50 at the nozzle 9 is preferably close to the stoichiometric gas/air ratio for the gas concerned. The air mixed with the combustible gas is preferably forced air, and preferably air having a pressure between 0.2 and 1 bar and preferably equal to about 0,6 bar. Moreover, again to ensure that the pilot flame generates the desired ionized current, the flame, at least at the terminal portion 24A of the rod 24, is advantageously substantially stable, i.e. is not influenced by external phenomena, for which purpose the box element 32 is provided, to form a chamber which protects the flame. For this purpose, the chamber preferably extends for a height H3 of between 1.5 and 5 times the height T1 of said terminal portion struck by the flame, and preferably equal to about 4 times this height. If the control unit senses that the pilot flame is absent, it automatically reignites it. For this purpose the control unit, via the cable 26 and the ignition member 25, generates a high voltage (for example between 5 kV and 10 kV and preferably equal to 7.5 kV) which is transmitted through the rod 24 as far as its point 24C. In this manner, because of the potential difference between the point 24C and the lower edge 35A of the sleeve element 35 (which is at earth) a spark is generated which ignites the combustible mixture exiting the nozzle 9, to form the desired pilot flame. Advantageously, by virtue of the fact that the terminal element can slide coaxially and is adjustable relative to the tubular element 7 as the terminal portion 24A of the rod 24 wears down, the end 24C of the rod can always be in the most suitable position by moving the terminal element upwards. Preferably the control unit operates in accordance with the following steps:
All the aforedescribed operations can be easily implemented in a control SW of a control unit of microprocessor type, which will not be described hereinafter. Advantageously the pressure of the gas and air fed to the pilot flame device are regulated, for example manually, to predetermined values, within a central feed unit, not shown, for said components. The gas feed to the pilot flame device is for example methane gas or the like. Finally it should be noted that the embodiment described up to this point is provided by way of example only, and that numerous variants are possible, all falling within the same inventive concept. For example, in a simplified version the pilot flame device could comprise only the flame sensing means and not also the automatic ignition means. According to a further variant the flame sensing and ignition means could be each formed with a dedicated member and not with a single member performing both functions, as described up to this point. For example, a rod of the previously described type or an equivalent element could be provided for the ignition means and another for the sensing means. Likewise the previously described rod 24 could be replaced by equivalent means, for example by flexible insulated electric cables connected to the ignition member 25 and to a metal tip of type similar to the terminal portion 24A of the previously described rod 24. The tubular element 2 could also be replaced by a dedicated conduit for the gas and one for the air which flow together and are mixed in a nozzle of similar type to that previously described. Finally it should be noted that the device arranged to generate a pilot flame for igniting an oxycutting device as heretofore described, and/or the oxycutting system comprising an oxycutting device and a device arranged to generate a pilot flame for igniting said oxycutting device as heretofore described are preferably used in a continuous casting plant, i.e. a plant in which the products to be cut are at a temperature greater than or equal to 700°C, but could also be used for cutting products at ambient temperature. |