CAPPED ELECTRIC LAMP AND LOW-PRESSURE MERCURY-VAPOR DISCHARGE LAMP

Abstract: A capped electric lamp comprises a cap which is secured to a light-transmitting lamp vessel having an electric element, which lamp cap is provided with a projecting contact pin (4) having an axis (11). An electric conductor (5) is connected to the electric element and the contact pin (4). The contact pin (4) is unilaterally deformed in an inward direction so as to form an indentation (15) for fixing the electric conductor (5). According to the invention, the electric conductor (5) in the contact pin (4) does not extend substantially beyond a boundary (16) of the indentation (15). Preferably, the indentation (15) has a pinch portion (17) for weakening the electric conductor during the deformation of the contact pin (4). Said pinch portion (17) preferably deepens at an angle alpha with respect to the axis (11), wherein 25 DEG ≤ alpha ≤ 45 DEG . In addition, the indentation (15) has a press portion (18) for fixing the electric conductor (5) in the contact pin (4).

Description: Capped electπc lamp and low-pressure mercury-vapor discharge lamp The invention relates to a capped electπc lamp compπsmg a light-transmitting lamp vessel accommodating an electπcal element, a lamp cap provided with a projecting contact pm having an axis, which lamp cap is secured to the lamp vessel, an electπc conductor which is connected to the electπcal element and to the contact pin, an indentation being formed in the contact pin to fix the electπc conductor The invention also relates to a low-pressure mercury vapor discharge lamp Such an electnc lamp is disclosed in GB-A 0 692 290 In the known lamp, wedge-shaped indentations are situated on either side of the contact pin and opposite each other, which indentations are used to shπnk the contact pin so as to contact the electπc conductor The known capped electπc lamp is a fluorescent lamp having two contact pins at the lamp cap In a fluorescent lamp, mercury is the pπmary component for (efficiently) generating ultraviolet (UV) light An inner wall of the discharge vessel may be coated with a luminescent layer compπsing a luminescent material for converting UV to other wavelengths, for example to UV-B and UV-A for tanning purposes, or to visible radiation foi general illumination purposes The discharge vessel of said fluorescent lamps is generally tubular with a circular cross-section and includes both elongated and compact embodiments A drawback of the known capped electπc lamp resides in that, duπng the manufacture of the lamp, more particularly when the contact pin is provided with the indentation, the end portion of the electπc conductor projecting from the contact pin is subjected to a pulling force to preclude that the electπc conductor in the lamp cap or in the lamp vessel electπcally contacts a further electric conductor which has been passed through an adjacent contact pm After fixing the electric conductor in the contact p , said projecting end portion of the electπc conductor must be removed This is achieved by cutting and/or filing This constitutes a drawback because additional safety measures must be taken to ensure that these operations are earned out in a safe and clean manner. In the case of the much used tubular fluorescent lamps compπsing two such lamp caps, which are each provided with two contact pins, said drawback increases accordingly. It is an object of the invention to provide a capped electπc lamp of the type mentioned in the opening paragraph, wherein said drawback is obviated. In accordance with the invention, this object is achieved in that the electπc conductor in the contact pin does not extend beyond a boundary of the indentation that is furthest removed from the lamp cap. The indentation in the contact pin is formed in the course of the manufacture of the electπc lamp by an inward deformation of the contact pin. By locally indenting the contact pin, the electπc conductor is fixed m the contact pin As a result of said indentation, the electπc conductor is weakened near the boundary of the indentation to such extent that, upon exerting a pulling force on the end portion of the electπc conductor projecting from the contact pin, the electπc conductor breaks off at a predetermined location By providing the electπc conductor with a predetermined weakened portion, the electπc conductor breaks off near the boundary of the indentation After breaking off the electπc conductor, (the end portion of) the electric conductor no longer projects from the contact pin. As a result, cutting and/or filing of the end portion of the electπc conductor projecting from the contact pin after fixing the electnc conductor has become superfluous It is to be noted that the exertion oi a pulling force on (the end portion of) the electπc conductor can alternatively be earned out, after fixing the electπc conductor in the contact pin, by suitably twisting the end portion of the electnc conductor projecting from the contact p Expenments have further shown that upon pulling loose the end portion of the electric conductor, the fixation resulting from the indentation of the contact pm is sufficiently strong, so that the end portion of the electnc conductor can be pulled loose independent of the fixation of the electnc conductor Indenting the contact pin to weaken the electnc conductor preferably takes place unilaterally The indentation is generally formed in the contact pm by means of a so-called pinching pin, which is pressed against the contact pin in a direction transverse to the axis, causing the contact pin to be deformed in an inward direction A prefeπed embodiment of the capped electnc lamp in accordance with the invention is charactenzed in that the indentation has a pinch portion near the boundary, which serves to weaken the electnc conductor duπng the manufacture of the electnc lamp. The term "pinch portion" is to be taken to mean in the descnption and the claims of the invention under consideration that, dunng the indentation process, the contact pin is locally pressed deeper into the electπc conductor and at a more acute angle. This pinch portion does not "cut" the electπc conductor but causes the electnc conductor to be weakened such that upon exerting a pulling force on the end portion of the electnc conductor, said electnc conductor breaks off at a predetermined location The use of such a pinch portion has the advantage that the electnc conductor remains fixed in the contact pin dunng and after the removal of the projecting end portion of the electπc conductor. Exerting a pulling force on the projecting end portion of the electπc conductor, after indentation of the contact pin, does not cause the fixation of the electπc conductor in the contact pin to be weakened such that the electnc conductor is no longer fixed in the contact pin In a particularly preferred embodiment of the capped electnc lamp in accordance with the invention, the pinch portion deepens in the direction of the front boundary at an angle ranging from 10° < α ≤ 45°, wherein the angle α is measured with respect to the axis. To fix the electnc conductor, use is made of a so-called pinching pin. At an angle α < 10°, the weakening of the electnc conductor dunng the provision of the indentation is insufficient to cause the end portion of the electnc conductor to become detached from the electπc conductor when a pulling force is applied, while at the same time the electπc conductor remains fixed in the contact pm Furthermore, at an angle α < 10°, the pulling force necessary to remove the end portion of the electnc conductor is so large that the fixation of the electπc conductor in the contact pm is annihilated almost completely. At an angle α > 45°, aging of the pinching pin occurs rapidly due to the fact that the pinch portion breaks off readily owing to too high a pressure on said pinch portion. Preferably, the pinch portion deepens at an angle in the range from 25° < oc < 35° Expenments have shown that the use of a pinching pin having such a pinch portion enables the end portion of the electnc conductor to be removed while preserving the fixation The indentation 15 further compnses a press portion for fixing the electπc conductoi The combination of the press portion and the pinch portion causes a synerge c effect to be obtained. On the one hand, the pinch portion weakens the electπc conductor upon indenting the contact pm and, on the other hand, the press portion causes the electπc conductor to be fixed in the contact pm such that the end portion of the electnc conductor can be readily pulled loose without the fixation of the electnc conductor being substantially reduced. To this end, the length of the press portion in the fixation area is preferably chosen to be such that upon pulling the end portion of the electnc conductor from the contact pin, the electnc conductor remains fixed in the contact pin. It is particularly favorable if the contact pin 4 has only one indentation 15. This enables the pinch portion and the press portion to be provided in a single operation. The measure in accordance with the invention can particularly suitably be applied to low-pressure mercury vapor discharge lamps compnsing a capped electπc lamp in accordance with the invention wherein the lamp vessel encloses a discharge space provided with a filling of mercury and an inert gas in a gastight manner, and wherein the electπc element compnses an electrode arranged in the discharge space for maintaining a discharge in said discharge space. These and other aspects of the invention will be apparent from and elucidated with reference to the embodιment(s) descnbed hereinafter. In the drawings: Fig 1 is a side view of a capped electπc lamp in accordance with the invention; Fig. 2 is a cross-sectional view of a contact pin of the capped electπc lamp in accordance with the invention; Fig. 3A is a cross-sectional view of the contact p before the indentation is provided, Fig. 3B is a cross-sectional view of the contact pm shown in Fig. 3A dunng the provision of the indentation, and Fig 4 shows the pulling force as a function of the relative depth dimension of the indentation The Figures are purely diagrammatic and not drawn to scale. Particularly foi clanty, some dimensions are exaggerated strongly In the drawings, like reference numerals refer to like parts whenever possible In Fig 1, the capped electnc lamp compnses a light-transmitting lamp vessel 1 accommodating an electnc element 2 A lamp cap 3 provided with a projecting contact pin 4 is secured to the lamp vessel 1 An electnc conductor 5 connects the electπc element 2 to the contact pin 4. The contact pin 4 is provided with an indentation 15 for fixing the electπc conductor 5. The lamp shown compnses two identical lamp caps 3, which each have two contact pins 4, said lamp caps each being connected by a respective conductor 5 to the electnc element 2. The lamp shown is a low-pressure mercury vapor discharge lamp, wherein the lamp vessel 1 encloses a discharge space 9 containing a filling of mercury and an inert gas in a gastight manner. The lamp vessel 1 is coated with a luminescent matenal (not shown in Fig. 1). The discharge space 9 accommodates two electrodes, which serve as the electnc element 2, and which can be heated by current passage in order to ignite the lamp. Fig. 2 is a cross-sectional view of a detail of the capped electnc lamp in accordance with the invention shown in Fig. 1. In particular, Fig. 2 diagrammatically shows a contact pin 4 with an axis 11, the electnc conductor 5 being fixed. The contact pin 4 is unilaterally deformed in an inward direction, an indentation 15 being formed in the contact pin 4 (see Figs. 3 A and 3B) The indentation 15 has a boundary 16 at a side facing away from the lamp cap 3. In the example shown in Fig 2, the boundary is indicated as a plane extending transversely to the axis 11 In an alternative embodiment, the boundary encloses an angle with the axis 11. In accordance with the measure of the invention, the electπc conductor 5 in the contact pin 4 does not extend beyond the boundary 16 of the indentation 15. The indentation 15 compnses a pmch portion 17 and a press portion 18. Near the boundary 16, the indentation has a p ch portion 17 for weakening the electnc conductor 5 in the course of the manufacture of the electπc lamp In the example shown in Fig. 2, said pinch portion 17 deepens in the direction of the front boundary 16 at an angle , said angle α being measured with respect to the axis 11 Preferably, the angle α lies in the range from 25° < α < 35°. A pinch portion 17 that deepens at an angle α ~ 30° is particularly favorable Preferably, the ratio of the depth d pι of the pinch portion 17 to the diameter d cp of the contact pin 4 meets the relation d 0 05 < -^ < 0.15 The indentation 15 further compnses a press portion 18 for fixing the electnc conductor 5 The press portion 18 makes sure that the electπc conductor 5 is appropnately fixed in the contact pin 4, while the pmch portion 17 so weakens the electπc conductor 5 when it provides the contact p 4 with an indentation that the end portion of the electπc conductor can be readily pulled loose Fig. 3A is a diagrammatic, cross-sectional view of the contact pin 4 before the indentation is provided. The contact pin 4 has a thickened end portion, which bears reference numerals 41 and 42 in this cross-sectional view. The electnc conductor 5 has an end portion 51, which projects from the contact pin 4. Furthermore, a so-called pinching pin 25 is embodied so as to compnse a so-called pmch portion 27 and a press portion 28. The pinching pin 25 is moved towards the contact pin 4 in the direction indicated by means of the arrow shown in Fig. 3A. Fig. 3B is a diagrammatic, cross-sectional view of the contact pin of Fig. 3A dunng the deformation of the contact pin 4 for providing the indentation. The pinch portion 27 and the pressing portion 28 of the pinching pin 25 are pressed into the thickened end portion 41 of the contact pm, thereby causing an inward, unilateral deformation of the thickened end portion 41. The deformation of the contact pin 4 causes matenal (metal) of the electnc conductor 5 to flow out, which is shown in Fig. 3B in that the electnc conductor 5 becomes thinner at the location of the indentation 15 The pinching portion 27 of the pinching pin 25 shapes the pmch portion 17 in the thickened end portion 41, and the pressing portion 28 of the pinching pin 25 corresponds to the press portion 18 m the thickened end portion 41 of the contact pin 4. Under the influence of the pinching portion 27 of the thickened end portion 41, the electnc conductor 5 is weakened at the location of the maximum indentation, referenced 52 in Fig. 3B, to such extent that a pulling force exerted on the end portion 51 of the electnc conductor 5 causes this end portion to break off near the boundary 16 of the indentation 15 After the end portion 51 has been detached from the electnc conductor 5, the situation as shown in Fig 2 is obtained Pin-pinching expeπments have shown that the pinch depth is a measure of the strength of the pinch joint. It has been found that a favorable ratio of the depth d pr of the press portion to the diameter d cp of the contact pin meets the relation- 0.2 < ^ < 0 4 d« In Fig 4, the pulling force F (in N) is shown as a function of the relative depth d pr /d cp of the indentation The pulling force F is the force that is necessary to pull the end portion 51 of the electπc conductor 5 loose from the contact pin 4 (see Fig. 3B) The relative depth d pr /d cp is also referred to as the pin-pinching depth In Fig 4, three kinds of symbols are used (a) open squares after pulling loose the end portion 51 of the electnc conductor 5, said electπc conductor 5 can be moved in the contact pin 4, (b) filled tnangle: deformation of the contact pm has caused the electπc conductor 5 to become detached on the side of the electπc conductor 5 facing the lamp vessel l; (c) filled diamonds the end portion 51 of the electπc conductor 5 breaks off and can be readily removed from the contact pin 4 In connection with this, broadly three ranges can be distinguished in Fig 4 (a) too small a pin-pinching depth d pr /d cp < 0 2 At a pin-pinching depth below the above-mentioned limit, the end portion 51 of the electπc conductor 5 does not break off, but instead the electπc conductor 5 moves in the contact pin 4 (b) too large a pin-pinching depth d pr /d cp > 0 4 At a pin-pinch g depth above said limit, the end portion 51 of the electnc conductor 5 can be readily removed from the contact pin 4 However, dunng the deformation, the indentation formed in the electnc conductor on the side facing the lamp vessel 1 is too deep, as a result of which the electπc conductor 5 may become detached on the lamp side (c) a favorable pin-pinching depth 0 2 < d pr /d cp < 0 4 At a pin-pinching depth in between said limits, the superfluous end portion 51 of the electnc conductor 5 can be readily pulled loose and removed The fracture in the electπc conductor 5 occurs near the spot where the indentation 15 is maximal, and which is referenced 52 in Fig 3B The electπc conductor 5 is sufficiently secured in the indentation 15 and there is no nsk that the electnc conductor 5 will be pulled loose on the side facing the lamp vessel 1 Fig 4 shows, by means of vertical dotted lines, a very favorable range for the pin-p ching depth In the range indicated by means of (1), the pin-pinching depth d pr /d cp meets the relation 0 25 < -^ < 0 35 d<> Preferably, the length l c ι of the fixation of the electnc conductor 5 in the contact pin 4 is at least 0 75 mm (see Fig. 2) It will be clear that, within the scope of the invention, many vanations are possible to those skilled in the art The scope of piotection of the invention is not limited to the examples descnbed herein The invention is embodied in each novel charactenstic and each combination of characteπstics Reference numerals in the claims do not limit the scope of the protection thereof The use of the verb "to compnse" and its conjugations does not exclude the presence of elements other than those mentioned in the claims. The use of the article "a" or "an" in front of an element does not exclude the presence of a plurality of such elements.

Claims: y CLAIMS: 1 A capped electnc lamp compnsing a light-transmitting lamp vessel (1) accommodating an electπcal element (2), a lamp cap (3) provided with a projecting contact pin (4) having an axis (11), which lamp cap is secured to the lamp vessel (1), an electnc conductor (5) which is connected to the electπcal element (2) and to the contact pin (4), an indentation (15) being formed in the contact pin (4) to fix the electnc conductor (5), charactenzed in that the electnc conductor (5) in the contact pin (4) does not extend beyond a boundary (16) of the indentation (15) that is furthest removed from the lamp cap (3). 2. A capped electnc lamp as claimed in claim 1, charactenzed in that the indentation (15) has a pinch portion (17) near the boundary (16), which serves to weaken the electnc conductor (5) dunng the manufacture of the electnc lamp. 3 A capped electnc lamp as claimed in claim 2, charactenzed in that the pinch portion (17) deepens in the direction of the front boundary (16) at an angle ranging from 10° < δ < 45°, wherein the angle α is measured with respect to the axis (11) 4 A capped electnc lamp as claimed in claim 3, charactenzed in that the pinch portion (17) deepens at an angle in the range from 25° < < 35° 5 A capped electric lamp as claimed in claim 1 oi 2, charactenzed in that the indentation (15) compnses a press portion (18) foi fixing the electric conductor (5) 6 A capped electπc lamp as claimed in claim 5, charactenzed in that the ratio of the depth d pr of the press portion (18) to the diameter d cp of the contact pm (4) meets the relation 0.2 < -^ < 0.4 d P 1. A capped electnc lamp as claimed in claim 1 or 2, charactenzed in that the length I d of the fixation of the electnc conductor (5) in the contact pin (4) is at least 0.75 mm. 8. A capped electnc lamp as claimed in claim 1 or 2, charactenzed in that the contact pin (4) has only one indentation (15). 9. A capped electnc lamp as claimed in claim 1 or 2, charactenzed in that the lamp has two lamp caps (3) which are each provided with two contact pins (4) 10. A low-pressure mercury vapor discharge lamp comprising a capped electπc lamp as claimed in claim 1 or 2, wherein the lamp vessel (1) encloses a discharge space (9) provided with a filling of mercury and an inert gas in a gastight manner, and wherein the electnc element (2) compnses an electrode arranged in the discharge space (9) for maintaining a discharge in said discharge space (9)

Inventors: DE BOT FRANK G C, SPAAPEN ANTONIUS J, VAN DUIVENDIJK PIETER D M, DE BOT, FRANK, G., C., SPAAPEN, ANTONIUS, J., VAN DUIVENDIJK, PIETER, D., M.
Applicants: KONINKL PHILIPS ELECTRONICS NV, KONINKLIJKE PHILIPS ELECTRONICS N.V.
Application year: 2001
Main classification: H01J5
IPC codes: H01J5