Electric incandescent lamp

Abstract: In the electric lamp according to the invention, the incandescent body (2) is connected to the current supply conductors (6) in such a way that an internal end portion (15) of the latter is inserted into an end portion (3) of the incandescent body. The internal end portion has a V-shape (16,17) with a free end (18). During assembly, the latter rattles over turns (13,12) in order to grip behind a turn (12) at a distance from the end turn (13). The end portion (15) may comprise a stop (19) against the incandescent body (2).

Description: The invention relates to an electric incandescent lamp comprising: a translucent lamp vessel which is sealed in a vacuumtight manner; a coiled incandescent body having end portions which each comprise several turns and an end turn, positioned in the lamp vessel; current supply conductors which each grip with an internal end portion thereof into a corresponding end portion of the incandescent body and issue from the lamp vessel to the exterior. Such an electric incandescent lamp is known from GB 1 340 778. For various reasons, it may be decided to dispense with the use of a, for example, straight leg of an incandescent body in order to conduct current to said incandescent body. Such a leg may, for example, have an insufficient rigidity for contributing to the positioning of the incandescent body, or it may dissipate too much energy, or it may reduce the manufacturing speed of the incandescent body. The British Patent referred to above describes current supply conductors which have a helically coiled portion which is screwed into or around a corresponding end portion of an incandescent body. The helically coiled portion may be tapering in shape in order to achieve the screw connection more readily. Current supply conductors are disclosed in this Patent which have a metal tape portion whose end portion has lateral sawtooth edges. This end portion is screwed into a corresponding end portion of an incandescent body. In many lamp types, such as that disclosed in the said British Patent, a current supply conductor consists of several portions: a metal foil which is enclosed in a seal of the lamp vessel, an external conductor connected to said foil and issuing from the lamp vessel to the exterior, and an internal conductor connected to said foil and fastened to the incandescent body. The foil usually is a few tens few hundred µm thick. As a result, the current supply conductor is slack. The incandescent body may also be slack and, in addition, long. It is difficult, therefore, to make a screw connection between the incandescent body and the two current supply conductors, especially to achieve this without causing damage. US 3 189 778 discloses an electric incandescent lamp in which the current supply conductors comprise a molybdenum portion inside the lamp vessel which is locally flattened. The molybdenum portion projects into a corresponding end portion of the tungsten incandescent body, while a few turns of said end portion are also flattened. The use of molybdenum inside the lamp vessel, however, may be disadvantageous, for example, if the lamp vessel contains a halogen or a halogen compound in order to achieve a regenerative cycle. Flattening of tungsten involves the risk of the material being torn. The invention has for its object to provide an electric incandescent lamp of the kind described in the opening paragraph which is of a simple and reliable construction and can be easily manufactured. According to the invention, this object is achieved in that the internal end portion of each current supply conductor comprises a first leg and a second leg connected thereto at an acute angle and having a free end, which second leg points with its free end to the end turn of the relevant end portion of the incandescent body and grips with its free end behind a turn at a distance from the said end turn. In the electric incandescent lamp according to the invention, the current supply conductors may be easily connected to the incandescent body in that they are pushed into the respective end portions thereof. During this, the second leg rattles with its free end over a number of turns of the end portion until the current supply conductor has reached its end position. Then the second leg grips with its free end behind the last turn over which it has just been passed. It is possible during assembly of the incandescent body with the current supply conductors to perform a screw motion, but this is not necessary. A simple translation is sufficient. This means a major simplification and speeding-up of this assembly, and thus of lamp manufacture. Moreover, the construction of the lamp is reliable. In a favourable embodiment, the first leg extends on either side of the free end of the second leg in the incandescent body and presses against turns of the incandescent body diametrically opposite said end. The position of the incandescent body around the current supply conductor is very stable then. Rotation of the incandescent body both in a plane through both legs and perpendicular to this plane are counteracted thereby. Very attractive is an embodiment in which the current supply conductor has a stop which butts against the corresponding end turn of the incandescent body. The current supply conductor short-circuits turns of the incandescent body. In the said embodiment it is determined beforehand how many turns will be short-circuited. The power of the lamp for a given design is achieved within narrow limits in this embodiment through accurate dimensioning of the current supply conductors and the incandescent body. Spread in lamp life for this design is thus considerably reduced, and quality is improved. The stop may be realised by means of a portion of the current supply conductor extending alongside the plane of the end turn. This portion may extend away from the second leg or towards the second leg. It is favourable if the current supply conductors each extend along a respective plane or together extend along one plane. This simplifies lamp assembly, especially if the current supply conductors are composite bodies with, for example, a foil with an internal and an external conductor welded thereto. The components may then be readily included in a jig in order to be welded in the correct position. If composite current supply conductors comprising a foil are used, the lamp vessel often consists of glass having an SiO₂ content of at least 95% by weight. The current supply conductors may alternatively be of uniform construction and the lamp vessel may be made of hard glass with a coefficient of thermal expansion which corresponds to that of the conductors. The lamp vessel in these cases may have a gas filling containing a halogen, for example, hydrogen bromide. Alternatively, the current supply conductors may be composite, for example, built up from wire portions, and the lamp vessel may, for example, be made of soft glass, such as is the case with lamps for general lighting purposes. Obviously, the essence of the invention is not affected by the nature of the lamp. The internal portion of the current supply conductors may be formed from wire or from plate metal, for example, which has been stamped into shape. The free end of the second leg is flattened in an embodiment, for example, in a plane through the first and the second leg. The area of the surface with which the second leg is in contact with a turn of the incandescent body is increased by this. An attractive aspect of the construction of the lamp according to the invention is that the incandescent body may be coiled around a flat or, for example, an oval mandrel instead of around a round mandrel, or around round mandrels such as in the case of a coiled-coil helical incandescent body. This is because the current supply conductors need not be rotated in order to come into engagement with the incandescent body. Embodiments of the electric incandescent lamp according to the invention are shown in the drawings, in which Fig. 1 shows a lamp partly in side elevation, partly in cross-section, Fig. 2 shows a detail of the lamp of Fig. 1 before (Fig. 2a) and after (Fig. 2b) assembly, Fig. 3a shows an alternative embodiment of the lamp in side elevation, Fig. 3b shows a detail of Fig. 3a, Fig. 3c shows a modification of Fig. 3b. In Fig. 1, the electric incandescent lamp comprises a translucent lamp vessel 1 of, for example, quarts glass, which is sealed in a vacuumtight manner and in which a coiled incandescent body 2 comprising end portions 3 is positioned. The incandescent body drawn is made of helically coiled tungsten wire. The incandescent body has a number of supports 4. The lamp vessel 1 has seals 5 through which current supply conductors 6 are passed, issuing from the lamp vessel to the exterior. In the lamp drawn, the current supply conductors 6 each comprise a foil 7 to which an external conductor 8 and an internal conductor 9 are welded. A ceramic lamp cap 10 is fixed to each of the seals 5 and has a contact 11 which is connected to the corresponding current supply conductor 6. The current supply conductors 6 have an internal end portion 15, which is integral with the internal conductor 9 in the Figure, and which grips into a corresponding end portion 3 of the incandescent body 2. The end portions 3 of the incandescent body 2 each have a number of turns 12 and an end turn 13 (Fig. 2). The lamp vessel is filled with inert gas and a halogen compound, i.e. argon and hydrogen bromide. As is apparent from Fig. 2, the internal end portion 15 of the current supply conductor 6, i.e. the internal conductor 9 thereof, comprises a first leg 16 and a second leg 17 which encloses an acute angle α therewith and which has a free end 18 by means of which said second leg points towards the end turn 13 of the incandescent body 2 (Fig. 2b) and by means of which the second leg 17 grips behind a turn 12 at a distance from the said end turn 13. As is apparent from Fig. 2b, the first leg 15 presses against turns 12 on either side of the free end 18 of the second leg 17 diametrically opposite this second leg. The internal end portion 15 has a stop 19 which butts against the end turn 13, so that the depth to which the end portion 15 can project into the incandescent body 2 is limited. The current supply conductors 6 extend in one plane in Figs. 1 and 2. The current supply conductor 6 and the incandescent body 2, when brought into opposition as shown in Fig. 2a, may be readily assembled in that they are moved rectilinearly towards one another. The free end 18 then rattles past turns 13, 12 until the stop 19 is checked by the end turn 13 or the translatory movement is stopped. In Figs. 3a and 3b, parts corresponding to parts in the preceding Figures have reference numerals which are 20 higher. The lamp shown has only one seal 25 through which both current supply conductors 26 are passed. In Fig. 3c, reference numerals are 20 higher than those in Fig. 3b. The free end 58 is flattened. The shape and the dimensions of the current supply conductors are chosen so as to correspond to the nature of the lamp in question. Those skilled in the art may easily ascertain a favourable configuration in a single experiment. In the lamp of Fig. 1, the incandescent body has the following characteristics: tungsten wire diameter 178 µm, internal diameter 1,17 mm, external diameter 1,52 mm. The internal end portion of the current supply conductor consisted of tungsten wire of 254 µm. The dimension h in Fig. 2a may be chosen to be fractionally larger than the internal diameter of the incandescent body or, if a flat mandrel was used, than the greatest internal diameter, for example, 20% greater. The dimension 1 of a stop, 19 in Fig. 2a, having the given shape should preferably amount to at least the external diameter of the incandescent body. This dimension in a favourable embodiment, however, is also greater, for example by 20%. In the lamp shown h and 1 were 1,4 and 1,8 mm, respectively. The angle α is favourably chosen to be between 35 and 55°.

Claims: An electric incandescent lamp comprising: a translucent lamp vessel (1) which is sealed in a vacuumtight manner; a coiled incandescent body (2) having end portions (3) which each comprise several turns (12) and an end turn (13), positioned in the lamp vessel; current supply conductors (6) which each grip with an internal end portion (15) thereof into a corresponding end portion (3) of the incandescent body and issue from the lamp vessel to the exterior; characterized in that the internal end portion (15) of each current supply conductor (6) comprises a first leg (16) and a second leg (17) connected thereto at an acute angle and having a free end (18), which second leg (17) points with its free end (18) to the end turn (13) of the relevant end portion (3) of the incandescent body (2) and grips with its free end (18) behind a turn (12) at a distance from the said end turn (13). An electric incandescent lamp as claimed in Claim 1, characterized in that the first leg (16) presses against turns (12) on either side of the free end (18) of the second leg (17), diametrically opposite said free end (18). An electric incandescent lamp as claimed in Claim 2, characterized in that the internal end portion (15) has a stop (19) which butts against the relevant end turn (13). An electric incandescent lamp as claimed in Claim 1, 2 or 3, characterized in that the current supply conductors (6) extend alongside a flat plane. An electric incandescent lamp as claimed in Claim 1, 2, 3 or 4, characterized in that the free end (58) of the second leg (57) is flattened in a plane which runs through the first (56) and the second (57) leg.

Inventors: LONGO OSCAR, RAO RAGNUNATHA, LONGO, OSCAR, RAO, RAGNUNATHA
Applicants: PHILIPS ELECTRONICS NV, PHILIPS ELECTRONICS N.V.
Application year: 1991
Main classification: H01K1
IPC codes: H01K1