Title of Invention

A METHOD FOR COOLING COILS AND AN EQUIPMENT FOR IMPLEMENTING THE SAME

Abstract

A method for cooling coils that have been annealed in a bell furnace having a base on which the coils are stacked, said base is covered by a gastight cover into which a gas circulated by means of a turbine is injected the furnace fitted with burners going over the cover, this method being characterized by the following steps: the cover of the furnace undergoes natural cooling, by removing the latter, until a temperature of the said cover of 400°C is obtained; next, th'e cover undergoes forced cooling by blowing ambient air until a gas temperature equal to or less than 550°C is obtained; next, the gas undergoes cooling by heat exchange until a cover temperature of the order of 200°C is obtained; and finally, the cooling of the cover is completed by spraying a coolant, such as water, onto the cover.

Full Text

ORIGINAL 646/MUM/2000 FORM 2 THE PATENTS ACT, 1970. [39 OF 1970] & THE PATENTS RULES, 2003 COMPLETE SPECIFICATION [See Section 10; rule 13] "A METHOD FOR COOLING COILS AND AN EQUIPMENT FOR IMPLEMENTING THE SAME" STEIN HEURTEY, a French company, of Z.A.I, du Bois de 1'Epine, 91130 Ris-Orangis, France, GRANTED 19/7/2005 The following specification particularly describes and ascertains the nature of the invention and the manner in which it is to be performed:- The present invention relates to a method for cooling coils and an equipment for implementing the same. The present invention relates to a method intended to reduce the cooling time of products, especially metal coils during annealing in a bell furnace. The technical problem solved by the present invention is that of limiting the total cycle time for annealing such products. In order to make the technical field of the present invention clearly understood, reference will firstly be made to Figure 1 of the appended drawings, which is a schematic sectional representation in a vertical) plane of known equipment for annealing coils 1 in a bell furnace. The coils 1 are stacked on a base 6 and are covered by a cover 2 which is fastened in a gastight manner to the base 6 by means of clamping means 7. A gas possibly containing a variable proportion of hydrogen is injected into the cover 2, in which the gas is forced to recirculate due to the effect of a turbine 4 placed at the bottom of the cover 2 driven by a motor 5. The bell of the furnace 3 goes over the cover 2, this furnace being fitted with burners 8 for heating the cover. In such known equipment, the coils 1 are heated mainly by convection between the gas and the surface of |i the coils and by conduction within the coils. The gas is heated mainly by convection by the cover 2, the latter being itself heated by the burners 8 of the furnace 3. After the heating phase, which is carried out according to a temperature cycle tailored to the desired heat treatment depending on the grade of material of which the coils are composed, the latter are cooled in the atmosphere down to a temperature at which they are prevented from being oxidized. This cooling is governed by the physical laws of convective heat exchange, particularly by the nature of the gas, its speed of circulation and its temperature. The nature of the gas and its speed may be regarded as already optimized, depending on the type of heat treatment to be carried out and on the high-temperature mechanical behaviour of the recirculating turbine 4 which limits the possible flow rates and speeds that can be obtained. The only means of improving the cooling of the coils therefore consists in obtaining as cold a gas as possible, at any instance, so as to create the largest possible thermal gradient in the coils, this gradient being the driving force fpr the conductive exchange flux in the coils. This cooling must take place, for each of its phases, so as not to expose the various parts of the furnace, its fittings or the products to thermal or mechanical stresses liable to imperil them. Therefore, the present invention relates to a method for cooling coils that have been annealed in a bell furnace having a base on which the coils are stacked, said base is covered by a gastight cover into which a . gas circulated by means of a turbine is injected, the furnace fitted with burners going over the cover, this method being characterized by the following steps: the cover of the furnace undergoes ' natural cooling, by removing the latter, until a temperature of the said' cover of 400°C is obtained; next, the cover undergoes forced cooling by blowing ambient air until a gas temperature equal to or less than 550°C is obtained; next, the gas undergoes cooling by heat exchange until a cover temperature of the order of 200°C is obtained; and finally, the cooling of the cover is completed by spraying a coolant, such as water, onto the cover. The present invention also relates to an equipment for implementing the above method, characterized in that it comprises a cooling bell fitted with forced-air cooling means, means for spraying a coolant onto the cover of the furnace, and an external circuit for cooling the gas contained in the cover. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS . There are four known means for cooling the gas contained in the cover 2 of a bell furnace as illustrated in Figure 1. These means are shown respectively in Figures 2, 4, 5 and 6, which are views similar to Figure 1. In. the cooling system illustrated in Figure 2, natural cooling is achieved by removing the bell 3 of the furriace and leaving the cover 2 to cool down freely in the air. The turbine 4 remains in operation during this cooling. This technique has the drawback of not allowing; high cooling rates to be obtained In Figure 3 of the!! appended dawings, which illustrates the variations in temperature of the cover as a function of time, curve 1 shows the change in the temperature of the cover (plotted on the y-axis) during this natural cooling.; As this curve 1 shows, . this technique does not make it Impossible to obtain high cooling rates. It has the advantage of using no additional equipment, but it is only effective at the start of cooling when the cover 2 is very hot. A second known cooling system is illustrated in Figure 4 In this system, during the cooling phase, the bell 3 of the furnace is replaced by a cooling bell 9 which is, fitted with a number of fans, such as 10, which blow the ambient air over the cover 2 so as - to make it cool down more quickly. The cover cooling curve obtained using such a system is shown schematically by 2 in Figure 3. It may be seen that, as in the case of the natural cooling (curve 1), such equipment is effective only when the temperature of the cover is high. When the temperature of the cover falls, the time needed to cool the coils is long. In order to make the coils cool down more quickly, it is possible to use a water spray on the cover 2. This technique is illustrated in Figure 5 which shows schematically a system for spraying a coolant, especially water, onto the cover 2 using coolant supply rails 15 and spray nozzles 16. This coolant spraying can only be employed when the cover 2 is at a temperature below about 200°C, for obvious reasons of mechanical behaviour. Such a restriction means that this cooling method can only be employed as a complement to other cooling techniques such as those described above with reference to Figures 2 and 4. Figure 3 shows, at 5, the cover cooling curve obtained by using the cooling technique described above with reference to Figure 5. Another cooling means is illustrated in Figure 6. It consists in using an external gas cooling circuit consisting of a heat exchanger 13 which cools the gas contained in the cover 2, for example by means of a circulation 14 of a coolant such as water, the gas being recirculated by means of a fan 12 and a circuit 11. This gas recirculation can be started only when the temperature of the gas is below about 500°C, so as to prevent any damage to the turbine of the fan 12 and to the exchanger 13. The cover cooling curve obtained by this means is shown by the curve 3 in Figure 3. The current practice employed is for the various cover cooling means described above to be used either separately or in combination. The object of the present invention is to combine these means so as to be able to use them successively during those phases of the cooling cycle in which they are the most effective. The desired aim of such a combination is to make it possible to reduce the total time required to cool the . coils and, by this means, to reduce the total cycle time for annealing the coils with this type of furnace, this reduction resulting in an increase in productivity. Consequently, the subject of the present invention is a method for cooling coils that have been annealed in a bell furnace having a base on which the coils are stacked, which base is covered by a gastight cover into which a gas circulated by means of a turbine is injected, the furnace fitted with burners going over the cover, this method being characterized by the following successive steps: - the cover of the furnace undergoes natural cooling, by removing the latter, until a temperature of the said cover of approximately 400o C is obtained; - next, the cover undergoes forced cooling by blowing ambient air until a gas temperature equal to or > less than approximately 550°C is obtained; and next, the gas undergoes cooling by heat exchange until a cover temperature of the order of 200°C is obtained; and - finally, the cooling of the cover is completed by spraying a coolant, such as water, onto the cover. - The subject of the present invention is also the equipment allowing the abovermentioned method to be implemented. One embodiment of this equipment, which is in no way limiting in character, is illustrated by Figure-7 of the appended drawings, which is a cross section similar to that in Figure 1. It may be seen that this equipment comprises the known cooling equipment described above with reference to Figures 2, 4, 5 and 6, that is to say forced-air cooling equipment 9 and 10, external heat-exchange cooling equipment 11, 12, 13 and 14, and coolant-spray cooling equipment 15 and 16. By virtue of this combination, the cooling cycle forming the subject of the present invention comprises the following steps: 1. Natural cooling of the cover 2 after the furnace 3 has been removed, this cooling step corresponding to curve 1 in Figure 3. It is employed for a time of about 15 to 20 minutes, during which the temperature of the cover reaches approximately 400°C. 2. Forced-air cooling by putting the cooling bell 9 into place and by turning the fans 10 on, this cooling step, which corresponds to curve 2 in Figure 3, being employed until a gas temperature equal to or less than approximately 550°C is obtained, at which temperature it is then allowed to start the fan 12 of the circuit 11 for cooling the gas by the exchanger 13, the gas being cooled by a circulation of water 14 for example. 3. Start of the water spray cooling 15 and 16 as soon as the temperature of the cover 2 reaches approximately 200°C. The cooling cycle thus obtained by the present invention is described by curves 1, 2, 3 and 4 in Figure 3, these curves clearly demonstrating the reduction in total time of the cooling phase obtained by virtue of the invention compared with the conventional means, the cooling rates of which are illustrated by the succession of curves 1, 2 and 3 or 1, 2 and 5. The saving in time obtained by implementing the present invention can be estimated to be between about 1 hour and 1 hour 30 minutes, something which represents a gain in productivity of the order of 4% over a total annealing cycle of 35 hours. Of course, it remains the case that the present invention is not limited to the embodiments described and/or mentioned above, rather it encompasses all the variants thereof. WE CLAIM: 1. A method for cooling coils that have been annealed in a bell furnace having a base on which the coils are stacked, said base is covered by a gastight cover into which a gas circulated by means of a turbine is injected the furnace fitted with burners going over the cover, this method being characterized by the following steps: the cover of the furnace undergoes natural cooling, by removing the latter, until a temperature of the said cover of 400°C is obtained; next, th'e cover undergoes forced cooling by blowing ambient air until a gas temperature equal to or less than 550°C is obtained; next, the gas undergoes cooling by heat exchange until a cover temperature of the order of 200°C is obtained; and finally, the cooling of the cover is completed by spraying a coolant, such as water, onto the cover. 2. An equipment for implementing the above method as claimed in claim 1, characterized in that it comprises a cooling bell (19) fitted with forced-air cooling means (10), means (15, 16) for spraying a coolant onto the cover (2) of the furnace, and an external circuit (11, 12, 13, 14) for cooling the gas contained in the cover. 3. The equipment as claimed in claim 2, wherein the external circuit for cooling the gas contained in the cover comprises a heat exchanger (13) which cools the said gas by means of a circulation (14) of a coolant, the gas being recirculated by a fan (12) in a circuit (11). 4. A method for cooling coils substantially as herein described with reference to the accompanying drawings. 5. An equpment for implementing the method substantially as herein described with reference to the accompanying drawings. Dated this 11th day of July, 2000. [RITUSHKA NEGI] OF REMFRY & SAGAR ATTORNEY FOR THE APPLICANTS

Documents:

646-mum-2000-cancelled pages(19-7-2005).pdf

646-mum-2000-claims(granted)-(19-7-2005).doc

646-mum-2000-claims(granted)-(19-7-2005).pdf

646-mum-2000-correspondence(23-3-2006).pdf

646-mum-2000-correspondence(ipo)-(23-1-2007).pdf

646-mum-2000-drawing(19-7-2005).pdf

646-mum-2000-form 1(11-7-2000).pdf

646-mum-2000-form 19(19-5-2004).pdf

646-mum-2000-form 2(granted)-(19-7-2005).doc

646-mum-2000-form 2(granted)-(19-7-2005).pdf

646-mum-2000-form 3(11-7-2000).pdf

646-mum-2000-form 3(19-7-2005).pdf

646-mum-2000-form 3(19-9-2000).pdf

646-mum-2000-form 5(11-7-2000).pdf

646-mum-2000-petition under rule 137(19-7-2005).pdf

646-mum-2000-power of authority(15-11-2000).pdf

646-mum-2000-power of authority(19-7-2005).pdf

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