Title of Invention	"METHOD FOR PRODUCING HELICALLY WOUND LUMINOUS ELEMENTS"
Abstract	The method is distinguished in that a thermal treatment of the incandescent wire at temperatures of over 1200°C takes place already before the winding of the incandes¬cent wire, so that, after separation/ the coil springs open and can easily be detached from the core wire.

Full Text

The present invention relates to method for producing helically wound luminous elements for an incandescent lamp. Technical field The invention proceeds from a method for producing helically wound filament elements, in particular incan¬descent elements, in accordance with the preamble of Claim 1. Furthermore, it is directed to incandescent elements produced according to this method. These are, in or coiled or else doubly wound or coiled luminous elements for incandescent , electrode coils lamps, or else electrode coils for pin electrodes of high- pressure discharge lamps. Prior art A, method for producing helically wound incandescent elements has already been disclosed in EP-A 149 282. Here, a number of incandescent elements are helically wound continuously from an incandescent wire onto a core wire. The incandescent wire (coil) wound onto the core wire is subsequently heated to approximately 1900 to 2200 °C in order to reduce stresses, for example by means of a, laser, high frequency or resistance heating of the core wire. During this, the incandescent wire is clamped on the core wire. The overall aim thereby is to minimize stresses in the coil. In order to extract the core wire from the wound incandescent wire, the coil is rotated relative to the core wire in the opposite direction. This complicated method is required because the inside dia¬meter of the coil is matched to the outside diameter of the core wire, and thereofore it cannot be avoided that the coil adheres to the core wire. A similar method with thermal treatment of the inc'an- descent wire to remove the stresses, and subsequent extraction of the core wire from the coil is also disclosed in DE-A34 35 323 3 and .JP-A 49-67 481\ The latter employs a lamp as means for heating the coil up to a temperature of between 600 and 900°C. Coils prepared in such a way do have a good dimensional stability. However, this has the very effect of preven¬ting simple extraction of the core wire from the coil. Description of the invention It is the object of the present invention to provide a method for producing helically wound filament elements, in particular incandescent elements, having a good dimensional stability, which is simple and time-saving and can therefore be mechanized particularly effectively. This object is achieved by means of the characterizing method steps of Claim 1. Particularly advantageous refinements are to be found in the dependent claims. In one embodiment, the method according to the invention for producing helically wound incandescent elements makes use of the technique, which is basically known per se, in which an incandescent wire made from high-melting material, usually tungsten, is wound onto a core wire and thermally treated, and subsequently separated and the core wire is extracted. The novel method proceeds in this case from the idea of thermally influencing the winding wire material as early as during the winding operation. By contrast with conven¬tional methods, in which the incandescent wire is likewise wound onto an endless core, in this case the subsequent stress-relieving operation on the core wire by continuous annealing is dispensed with. In particular, it must be ensured in this case that the radius of curvature of the reel onto which the incandescent wire is subsequently wound after the heat treatment is small by comparison with the axial length of the incandescent elements to be produced therefrom. In a particularly preferred embodiment/ the coils are separated directly after being wound, with the result that it is possible to dispense with reeling up. On the one hand, winding produces a permanent plastic deformation beyond the tensile yield point of the winding material, because the winding material must be bent to the radius of the core material, and this imposes a bending stress. On the other hand, the winding process additionally imposes on the winding material an elastic deformation reaching to the tensile yield point of the winding material, the so-called torsional stress. There is a super imposition of bending stress and tor¬sional stress during winding. The elastic residual stress component (bending and torsion) is released after the separation, and is seen, on the one hand, in the way the coil springs open to a larger inside diameter. The incandescent element remains dimensionally stable in this case, that is to say is helically wound. On the other hand, the plastic residual stress component is seen in the reduction in the number of the wound turns in con¬junction with maintaining the axial length (comparable to the opening of a spring in the elastic region of the spring material). It has emerged, surprisingly, that it is even possible to ensure an adequate thermal treatment of the winding material directly before the winding operation, speci¬fically without appreciable loss in the customary winding speeds. Particularly when using a plasma torch for the thermal treatment, the energy transfer is so high that speeds of revolution of 10,000 rpm (revolutions per minute) and higher can be reached. Typical values are 6000 to 8000 rpm. The first method step consists according to the invention in that the incandescent wire is thermally treated. In the case of the production of incandescent elements, the incandescent wire must be brought to a temperature of up to near the recrystallization temperature of the material. A temperature in the region of between 60 and 90% of the recrystallization temperature is preferably suitable for this. In the case of tungsten, this means that the incandescent wire is brought to a temperature of more than 1200°C, preferably to more than 1400°C. The recrystallization temperature of tungsten is at about 1800C [sic]. At temperatures above 1800°C, a range is entered in which the tungsten sintered material begins to recrystallize, which is seen in increasing embrittlement. The material thereby becomes fragile. As a result, however, in the case of further processing (mounting of retaining rings or end pieces on the filament or long-drawing of the filament element) a high number of rejects would have to be expected. In a second embodiment, by contrast, the production of electrode coils electrode coils requires still higher temperatures, which are preferably in the region of the recrystallization tem¬perature, because the imposed stresses are not intended to be released any longer in this case. A certain recrystallization is thus desired. Immediately thereafter, the heated incandescent wire or filament element is wound onto the core. In order to prevent a marked cooling of the coil thus produced, the coil is heated directly in the vicinity of the core. Here, the term core covers both core wires and solid core pins. In the next step, the coil, which is still hot but already slightly cooled, is separated. If the coil is still too hot before the separation, its colour is tarnished or oxidation can occur. In the most unfavourable case, the coil springs open too little or not at all. Again, the so-called useful life of the core depends thereon. In this case, the finished coil still has, during separation, a residual stress, which is converted immediately after the separation into an enlargement of the inside diameter of the coil, with the result that the coil loses the intimate contact with the core wire. It now is seated only loosely on the core wire. For this reason, finally, it is easy in a last method step to extract the core wire from the coil seated loosely thereon. It is preferred in both embodiments to perform the thermal treatment of the winding wire by means of a plasma torch. The principle of such a plasma torch is described in more detail, for example, in NL-A 71 12 767. Argon, helium, hydrogen, nitrogen and their mixtures, for example, can be used as plasma. It has proved to be particularly suitable for the present purposes that the plasma combustion is performed in the free gas flow, argon, an argon/nitrogen mixture or an argon/hydrogen mixture being applied in particular. In particular, nitrogen can also be used as inert-gas cone. It is advantageous for both the anode and the cathode of the plasma torch to be located in the torch housing. The incandescent wire is advantageously to reach a temperature of more than 1200°C before winding. Since an exchangeable core (machine core) stabilizes the winding process and minimizes tolerances in the winding process, it is particularly well suited as the core. It is to be recommended in this case that the machine core consists of material, such as spring steel or tungsten, for example, which can be subjected to a high thermal load (in the temperature range around 1800°C) . The machine core should effectively endure temperatures of up to more than 1800°C. The material of the winding wire is typically tungsten, which can possibly be doped with additives such as potassium, silicon, aluminium and/or thorium. The present invention also comprises incandescent elements or electrodes having electrode coils which are pro¬duced according to the method described above, as well as lamps produced therefrom. As a result of the novel method, in the production of incandescent elements the stress introduced into the coil by the winding operation is influenced as a consequence of the thermal treatment undertaken shortly in advance precisely to the effect that the coil is able to spring open radially after the separation as a consequence of the stored mechanical energy. The elastic residual stress component described above is precisely the process of springing open radially. Because of this, the coil is detached automatically from the core wire, by contrast with the prior art, in which this method step presents the greatest problem. A particular advantage is the surprising property that the coil remains virtually dimensionally stable in the axial direction. The process of springing open axially is, similar to that of the opening of a spring, also elastic, and is seen in the reduction of the wound turns in conjunction with maintaining the prescribed winding length. In the present invention, the small axial residual stress is seen in the fact that it effects only a slight spread in the total length of the helically wound incandescent element. The temperature at the thermal pretreatment is now selected precisely such that the desired final inside diameter of the coil is produced automatically by the process of springing open radially after the separation. In the particular individual case, the precise dimensioning is a function essentially of the diameter of the core material and winding material, of the tempera¬ture and also of the winding speed. The enlargement of the inside diameter of the coil, occasioned by the process of springing open radially, is specific to type and varies in a range from 2 to 30%. In other words, the desired dimensions of the coil can be achieved with a smaller core wire compared to the prior art. The method according to the invention is basically suitable for two different applications: firstly, it can be used to produce for incandescent lamps luminous elements which are singly or doubly wound. In (coiled filament) the case of the singly wound luminous (coiled filament) the method can be applied directly as described. In the case of the doubly wound luminous element(coiled coil filament) the method must be modified by using a conventionally pro¬duced endless primary coil, which is still wound on a core wire, as core wire for a secondary coil. The method described above is then applied to produce the secondary coil. Thereafter, the further processing steps are then performed, or the primary core is immediately extracted. The method is suitable for all known diameters of the core wire or incandescent wire, and can be applied to all pitches or known pitches or leads. Because of the increasing surface adhesion, with decreasing diameter of the incandescent wire and core wire a. tendency is observed for the incandescent wire to adhere to the core wire. A remedy is provided here by a periodically alternating use of a plurality of corewires. Depending on the load, use is made in this case of 5 to 50, or even more core wires or core pins. This so-called revolver technique permits a longer period of use (useful life) of a machine core. Revolver technique is understood as automatically feeding a material before the (n+1)th process step, but after the preceding n-th process step has been completely executed. In the case of a revolver, this corresponds to automatic feeding of the next cartridge chamber together with contents after a shot has been fired. Winding material at an increased temperature onto a machine core increases the temperature of the machine core over its period of use until a steady-state tempera¬ture equilibrium is produced between the machine material, winding material and the ambient temperature. With increasing temperature of the machine core, its stability decreases, that is to say it becomes softer and more unstable (harder and more brittle in the case of sintered materials) , becoming more sensitive for the overall process, as a result. By applying the revolver technique, the individual core is capable of cooling again during the useful life of the other cores alterna¬tively employed (typically 5 to 50 cores). It is possible thereby to achieve a substantially longer useful life and also a smaller spread in the geometry of the coil. A second field of application is pin electrodes with applied electrode coils Such electrodes are disclosed, for example, in US-A 3 067 357. According to the method of the invention, such electrodes can be produced by applying particularly high temperatures, which are in the region of the recrystallization temperature of the material employed, in the thermal treatment of the winding wire. In the case of tungsten, the temperatures are preferably around or slightly above 1800°C. The elastic residual stresses, which cause the electrode coils to spring open, are thereby prevented. The winding wire can be "permanently burned" on the core pin or electrode shaft in this way. This increased temperature effect produces a. balance between the elastic residual stresses and the chemical and structural conditions. The imposed stresses are nothing other than a forced minimal change in the crystal lattice of a grain or crystallite/ which are also reflected in the bond lengths, bond angles and bonding forces. With each increase in the temperature of a material, the position of the atoms in the crystal lattice is further smeared, that is to say their position becomes ever more unfavourable in terms of energy for a special structure up to the reversible phase transfor¬mation (for example transformation of the ot phase of a crystal into the ß phase), a different structure, more favourable in terms of energy, being adopted from a specific temperature for the prevailing conditions. The sum of the microscopic lattice distortions produces the macroscopic residual stress component. By contrast with the winding of incandescent elements (at 1200-1800°C in the case of tungsten), the production of electrodes with electrode coils by the method according to the invention therefore requires a larger energy transfer (corresponding to a temperature of above 1800°C for tungsten, which is thus in the region of recrystalli-zation), so that the residual stress component is not elastically imposed by lattice distortions, but the stresses are compensated by a. structural "reorganization" of the lattice components (partial recrystallization or complete recrystallization) accompanied by maintenance of the natural structure. In general, in the case of winding electrode coils onto electrodes the plasma temperature is preferably set such that the temperature of the winding material comes approximately into the region of the so-called solid/liquid transition. The material is thus deformed in a soft state and the bonding distances in the lattice are relatively large, and thus the bonding forces are relatively small. After the shaping process step, which is carried out very quickly, the material has sufficient time to form a new structure by partial or complete recrystallization without the imposition of stresses into the lattice. The original structural type of the crystal lattice is maintained in this process. With increasing cooling time, the bonding conditions are normalized again, and the electrode coils is seated without stress (permanently burned) on the electrode shaft. In the prior art, holding the electrode coils on the pin has to be realized by welding or by a press fit. This addi¬tionally required welding step causes a similar struc¬tural change to the operation described above, but only in the region of the welding zone. The press fit is the reversal of the technique of winding incandescent elements. Specifically, an elastic electrode coil is subsequently provided with a core pin whose outside diameter is larger than the inside diameter of the electrode coil. The electrode coil is widened in the process. The elastic deformation produces a resilient force due to the feeding of the pin. The pin is thus secured by the friction of the individual turns. In known electrodes, therefore, the electrode coils is normally pushed on and then welded to the core pin, or the core pin is subsequently pushed into the electrode coils (press fit) . In the method according to the invention, however, there is no need either for welding or pressing in, since the electrode coil is held effectively on the core wire by itself. In particular, there is no longer a possibility of point-size damage to the electrode (embrittlement) , as could not be avoided in the case of the welding operation. It is possible by using the method according to the invention to achieve very high setting powers, if the entire method is taken into consideration. It is true that by comparison with other machines which do not undertake separation of the coil during winding (so-called lasso machines, see DE-A 16 39 095), the setting power is lower during winding. However, in return, the time expended for all subsequent method steps is substan¬tially shorter, and a range of method steps is eliminated completely, in particular the troublesome extraction of the core wire. Also eliminated are the provision of an endless winding core, as well as the annealing for dimensional stability as a separate method step, and the subsequent separating process. Accordingly, there is provided method for producing helically wound luminous elements for an incandescent lamp, in which a winding wire suitable for later use as incandescent wire and made from high-melting material of the kind such as herein described is wound onto a core which is formed from a core wire or a machine core, and thermally treated, and possibly, subsequently separated, and, the core is extracted, characterized in the following steps: a) a segment of the winding wire is firstly thermally, treated, as a result of which said segment is brought to temperatures below the recrystallization temperature of the material employed, specifically betweerf" 60 and 9.0%>pf this recrystallization temperature, b,} the winding wire is wound onto the core immediately thereafter, c) the winding wire is subsequently separated to form an incandescent wire, the finished coil still having during separation a residual stress which is converted immediately after separation into an enlargement of the inside diameter of the coil, with the result that the coil loses the intimate contact with the core, d) and finally, the core is extracted from the coil, which is seated thereon loosely. Figures The aim below is to explain the invention in more detail with the aid of a plurality of exemplary embodiments; in the figures: : Figure 1 shows a diagrammatic representation of the winding operation; Figure 2 shows a halogen incandescent lamp with a singly wound incandescent element; Figure 3 shows a doubly wound incandescent element for incandescent lamps; Figure 4 shows a pin electrode with a burnt-onel ectrode coils BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Figure 1 shows the parts of a winding machine which are important for the present invention. A displaceable machine core 1 made from spring steel is guided at one end in a holder 2a, and at the other end in a mating holder 2b. It can be retracted in the holder 2a, or extracted therefrom. In another embodiment, a fixed machine core and a moving wire feed unit can also be used. Coining as winding material from a supply reel 6 whose axis 8 is arranged parallel to the machine core 1, an incandescent wire 3 is wound by means of a wire feed (not represented) onto the machine core 1 to form a coil 13, while maintaining a prescribed lead which is set by means or a/lead drive 9. Shortly before a section of the incandescent wire 3 meets the machine core I/ it is thermally treated by means of a plasma torch 4. The plasma heating is performed in the free gas flow by means of an argon plasma 5. The plasma torch operates only when a winding drive 12 and the lead drive 9 are active. Once the prescribed length of a luminous element has been wound, a wire cutter 7 comes into action and cuts the luminous element to length. The luminous element springs open and can easily be stripped off, while the machine core 1 is returned. The wire feed restarts immediately thereafter, and the plasma torch comes into action again. A suitable machine control with appropriate drives (here, a Siemens Standard CNC control) ensures the combination of winding process and simultaneously performed thermal treatment of the winding material as a function of the speed. The productivity of the invention is to be seen in that even complicated filaments can be produced. For example, in accordance with Figure 2 it is possible to produce a singly wound luminous element 10 for tubular lamps 20 (halogen incandescent lamps) with four luminous segments (approximately 70 narrow turns in each case) and three interruptions situated therebetween (five wide turns in each case) as well as two ends (eight wide turns in each case). In this case, the machine core consists of spring steel with a diameter of 1.4 mm. The entire clamped length is more than 50 mm. The diameter of the incan¬descent wire is approximately 120 µm. Figure 3 is a diagram of a doubly wound luminous element 11 whose secondary coil is produced by the method accor- ding to the invention. The luminous element consists of tungsten in all the exemplary embodiments. Shown in Figure 4 is an electrode 13 which comprises a core pin or electrode shaft 18 and an electrode coils 19 wound electrode coil thereon. The electrode coils 19 is permanently burned on the core pin 18. WE CLAIM; 1. Method for producing helically wound luminous elements for an incandescent lamp, in which a winding wire (3) suitable for later use as incandescent wire and made from high-melting material of the kind such as herein described is wound onto a core which is formed from a core wire or a machine core (1), and thermally treated, and possibly, subsequently separated, and, the core is extracted, characterized in the following steps: a) a segment of the winding wire (3) is firstly thermally treated, as a result of which said segment is brought to temperatures below the recrystallization temperature of the material employed, specifically between 60 and 90% of this recrystallization temperature, b) the winding wire (3) is wound onto the core (1) immediately thereafter, c) the winding wire is subsequently separated to form an incandescent wire, the finished coil still having during separation a residual stress which is converted immediately after separation into an enlargement of the inside diameter of the coil, with the result that the coil loses the intimate contact with the core, d) and finally, the core is extracted from the coil, which is seated thereon loosely. 2. Method as claimed in claim 1, wherein the thermal treatment is performed by means of a plasma torch (4). 3. Method as claimed in claim 2, wherein the plasma combustion is performed in the free gas flow (5), an argon/nitrogen mixture or an argon/hydrogen mixture being applied, in particular. 4. Method as claimed in claim 1, wherein the core is an exchangeable machine core. 5. Method as claimed in claim 4, wherein the machine core consists of material such as herein described which is to be subjected to a high thermal load. 6. Method as claimed in claim 4, wherein the extraction of the core wire is performed by retracting the machine core. 7. Method as claimed in claim 1, wherein in the method step a) the winding wire is brought to temperatures in the vicinity of the solid/liquid transition. 8. Method as claimed in claim 1, wherein the material of the winding wire is tungsten. 9. Method for producing helically wound luminous elements substantially as herein before with reference to and as illustrated in the accompanying drawings.

Documents:

3691-del-1997-abstract.pdf

3691-del-1997-claims.pdf

3691-del-1997-correspondence-others.pdf

3691-del-1997-correspondence-po.pdf

3691-del-1997-description (complete).pdf

3691-del-1997-drawings.pdf

3691-del-1997-form-1.pdf

3691-del-1997-form-13.pdf

3691-del-1997-form-19.pdf

3691-del-1997-form-2.pdf

3691-del-1997-form-3.pdf

3691-del-1997-form-4.pdf

3691-del-1997-form-6.pdf

3691-del-1997-gpa.pdf

3691-del-1997-petition-137.pdf

3691-del-1997-petition-138.pdf

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