Abstract:
An electric lamp with a base ( 6 ), which is structurally subdivided into an upper part ( 7 ) that retains the bulb and a substantially circular-cylindrical lower part ( 5 ) for external fastening, which lower part protrudes past the upper part, and the protruding portion ( 13 ) is embodied as a detent mechanism for the external fastening. The detent mechanism in each case includes an inward-facing detent protrusion ( 20 ) located on the outside, which is an integral component of the lower part, and a metal spring ( 24 ), located opposite the detent protrusion and cooperating with it, that is secured in the lower part.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a U.S. National Phase Application under 35 USC 371 of International Application PCT/DE00/02205 (not published in English) filed Jul. 5, 2000. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to an electric lamp and more particularly relates to incandescent bulbs for use in the automotive field, especially in headlights. 
     BACKGROUND INFORMATION 
     From International Patent Disclosure WO 99/28949, an electric lamp is already known that is suitable for use both as a turn indicator or brake light in the tail region and as a turn indicator in the front headlight. The lamp uses a base of plastic with fastening tabs integrally formed on in a V, which form a receptacle for a peglike socket or plug part. 
     A further refinement of this lamp is described in German Patent Application DE-PA 198 43 506. The base has two resilient tabs, each provided with a detent protrusion, and a fastening ring supported rotatably about the annular axis of the base. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is the object of the present invention to furnish an electric lamp that creates a simple connection which can easily be undone again, and that functions reliably over a long service life. It is a further object of the invention to furnish an electric lamp with an improved lamp base that enables simple mounting of the lamp in the lamp socket. 
     Initial attempts to make the entire lamp base out of plastic have not proven themselves, because the effect of a plastic detent mechanism decreases over time. This detent mechanism has therefore been improved with the aid of a metal spring. In a first embodiment, a spring wire bent into a clip is advantageously used; the ends of the wire are let into the plastic wall of the base. In a further especially preferred embodiment, a sheet-metal spring embodied as a stamped and bent part is used. 
     The electric lamp according to the invention has a luminous filament (incandescent body or discharge arc) that is surrounded by a lamp bulb, and also has a lamp base in which the bulb is secured, as well as electrical base contacts and power supply leads for supplying power to the luminous filament. 
     The base comprises a frustoconical upper part, which surrounds the lamp bottom (typically embodied as a pinch), and a lower part secured to it, which protrudes partly past the circumference of the upper part and which in the region of the protruding portion has two detent mechanisms for fastening in the reflector. 
     The detent mechanisms each comprise a detent protrusion located on the outside and facing inward, which is an integral component of the lower part and a metal spring located opposite the detent protrusion and cooperating with it and secured in the lower part, the metal spring being suitable for locking in detent fashion in a recess on the reflector, while the detent protrusion is suitable for unlocking this locking of the metal spring again. 
     The above characteristics make simple mounting of the lamp in a reflector with a neck (or some other fastening means) possible. The locking can be undone again easily and reliably. The lamp is thrust into the reflector as far as the reference plane. After that, still further force must be exerted on the two protruding portions of the base, in order to deform the springs and bring about the locking in recesses of the reflector neck. As a result, force that keeps the lamp in the reflector always prevails at the spring. 
     In addition, the base on its underside advantageously has a recess for receiving a peglike socket part or plug part. As a result, the lamp of the invention is suitable for mounting on a lamp socket embodied as a plug. 
     In detail, the present invention relates to an electric lamp, which defines an axis A, having a bulb which contains a luminous filament, and having a base in which the bulb is fixed, the base being provided with external contacts, and having at least two power supply leads which electrically conductively connect the luminous filament to the contacts. The base is subdivided into an upper part, which retains the bulb an essentially circular cylindrical, and a lower part for external fastening, and the lower part protrudes past the upper part and the protruding portion is embodied as a detent mechanism for the external fastening. The detent mechanism in each case comprises a detent protrusion located on the outside and facing inward, which is an integral component of the lower part, and a metal spring located opposite the detent protrusion and cooperating with it and secured in the lower part. The metal spring is suitable for locking in detent fashion in a recess on the reflector, while the detent protrusion is suitable for unlocking this locking of the metal spring again. 
     The detent protrusion advantageously has a radially inward-pointing projection, which is connected to a base part via two chamfers. 
     In an especially preferred embodiment, the metal spring comprises a retainer element connected to the lower part of the base via an anchoring means and a spring part formed of two legs, and the retainer element is at least in part located approximately in the plane transverse to the lamp axis. A first, short leg is integrally formed onto the retainer element, and a second, long leg is attached at an acute angle to the free end of the first leg in such a way that it extends approximately parallel to the lamp axis. 
     In particular, an outward-pointing (away from the axis) projection, located approximately opposite the projection of the detent protrusion, is seated on the free end of the second leg, so that the unlocking is done by pressing the projection of the outer detent protrusion into the recess in which the projection of the second leg is seated. 
     In a first embodiment of the invention, the metal spring is embodied as a sheet-metal spring part, with a flat base plate transverse to the lamp axis as a retainer element and with a spring part formed in the shape of a V of two legs, and a first, short leg is attached to the base plate and is inclined relative to the base plate. A second, long leg is attached at an acute angle to the first leg and penetrates the plane of the base plate in such a way that it is again oriented approximately parallel to the lamp axis. The anchoring means may be realized by means of bores in the base plate. 
     In a second embodiment of the invention, the metal spring is embodied as a spring wire piece, and the retainer element has a base part approximately transverse to the lamp axis and the anchoring part is an extension of the base part, which is attached to the base part and is oriented parallel to the lamp axis, and the short leg is bent backward on the base part by more than 120°, in particular by approximately 180°. Preferably, the long leg is attached laterally to the short leg, in particular with an offset bend. This has the advantage that the spring travel distance is lengthened, and furthermore a stabilizing part between symmetrical first legs can be better secured. 
     Very good results with economical use of material are attained with an embodiment in which the spring wire piece is constructed symmetrically of two halves, both long legs of which are connected to one another via a connecting piece that forms the projection. An especially reliable locking is attained in that the connecting piece has a curved piece bent backward toward the second legs. 
     The functional safety and reliability is further enhanced by the provision that the two first legs of the symmetrical spring wire piece are connected to one another via a stabilizing part. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described in further detail below in terms of a plurality of exemplary embodiments. Shown are: 
     FIG. 1 a  shows, an electric lamp in side view; and FIG. 1 b  is the electric lamp of FIG. 1 a  rotated by 90; 
     FIG. 2, the lamp of FIG. 1 in section shows in cooperation with a reflector; 
     FIG. 3 a , a bottom view of the base of the lamp FIG. 3 b  is a perspective view of the metal spring of the lamp; 
     FIG. 4 a  shows, a further exemplary embodiment of a base with a spring wire piece in a plan view from below FIG. 4 b  shows the embodiment of FIG. 4 a  in section; 
     FIG. 5 a perspective view of the metal spring of FIG. 4 a ; and 
     FIG. 6 a  is, a perspective view of the base of FIG. 4 a  obliquely from above; and FIG. 6 b  shows the base of FIG. 4 a  obliquely from below. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In FIGS. 1 a ,  1   b ,  2   a  and  2   b , an electric lamp in accordance with a first exemplary embodiment is shown. This lamp has a lamp bulb  1  (of hard glass or quartz glass) which is closed at one end, from whose end which is closed with a pinch  2 , two power supply leads  3  protrude to the outside, which are connected electrically conductively with an incandescent body  4  located inside the lamp bulb  1 . The incandescent body  4  defines a vertical lamp axis A. The pinch  2  of the bulb  1  is fixed in a base  6  made of plastic. The base comprises a frustoconical upper part  7  and a substantially circular-cylindrical lower part  5  attached to it. On the top of the upper part  7  oriented toward the bulb  1 , the base  6  has an upper recess  8 , in which the pinch  2  of the bulb is fixed. The lower part  5 , on its underside, has a lower recess  9  for receiving a peglike socket or plug part. Two spatulate electrical contact lugs  10  are located in the recess  9 . These contacts made the electrical in the recess  9 . These contacts make the electrical connection between the plug (not shown) and the power supply leads  3 . 
     The lamp of the preferred exemplary embodiment described above is a brake light or turn signal lamp for a motor vehicle. This lamp is universally usable in the motor vehicle. It can be mounted as a turn signal lamp in a front headlight of the motor vehicle or as a turn signal or brake light lamp in a taillight of the motor vehicle. 
     The upper part and the lower part of the base can be formed integrally of a single workpiece or can be subdivided into two separate parts. 
     Preferably, the lamp is installed in a headlight (see FIG. 2 b ) equipped with a reflector  11 . To install the lamp in the back reflector opening  12  of a motor vehicle headlight, the lamp is first secured in the upper recess  8  of the base. 
     As shown in FIG. 3 a , the lower part  5 , on two opposite sides, has a respective lug part  13 , which protrudes markedly toward the upper part  7 . These two lugs  13  each form one detent mechanism for fastening to the reflector, or more specifically to an annular collar  15 , which has two opposed, for instance rectangular, recesses  14  (see FIG. 2 b ). The collar  15  is integrally formed onto the reflector neck  16  or secured to it. The recesses  14  cooperate with the detent mechanism of the base to make a separable connection. 
     The detent mechanism comprises a radially outer detent protrusion  20  (FIG. 2 b ) with an axially parallel base part  21  adjoining the lower part, and a radially inward-pointing projection  22  on the free end of the base part, which is connected to the base part  21  via two chamfers  23 . 
     The detent protrusion  20  cooperates with a metal spring  24  of spring sheet metal facing it. It comprises a flat retainer element  25  (FIG. 3 b ), which on the outside has two fins  26  with bores  27 . The latter serve as anchoring means for fastening to the underside of the lower part, for instance by ultrasonic welding, in which softened plastic material penetrates the bores  27 . 
     Seated between the fins  26  is a first, short leg  28  of a spring part that is integrally formed onto the retainer element  25  but is bent downward, away from the bulb, out of the plane of the retainer element. The angle of inclination is approximately 30°. A second, long leg  29  is integrally formed at an acute angle onto the free end of the first leg. It pierces the plane of the retainer element and extends approximately parallel (inclined slightly outward) to the lamp axis in the direction of the bulb. A radially outward pointing projection  30  is integrally formed onto the free end of the second leg and is located approximately opposite the projection  22  of the detent protrusion  20 , in spaced-apart fashion. The projection  30  is preferably bent back toward the second leg  29  (see FIG. 3 b ). 
     In FIG. 2 b , the lamp is attached to the collar  15  of the reflector and thrust axially into the opening of the reflector. In the process, the two metal springs  24  with their projection  30  lock in the recess  14  of the collar. This locking can be undone again by pressing the two detent protrusions  20 , seated on the outside, inward. As a result, the projections  30  are released again from the recess  14 . The detent protrusion  20  is prevented by its own spring force from catching in the recess  14 , since the detent protrusion springs back outward again. The chamfer  23  additionally facilitates the springing back of the detent protrusion  20 . 
     In a second embodiment (FIGS. 4 a  and  4   b ), the metal spring is a spring wire piece  31 . It is constructed symmetrically of two halves. The retainer element is a portion which comprises a base part  32 , located approximately in the plane transverse to the lamp axis, and an anchoring part  33  bent approximately 90° from it, and which is accommodated in the wall of the lower part  5  in an axially parallel bore. For the sake of better spring action, the base part  32  is inclined by about 10° from the plane of the bottom of the lower part. A short leg  34  attached to the base part is bent back by 140° toward the approximately equal-length base part  32  and merges with a long leg  35 , which is attached to the short leg in such a way that it extends back again approximately axially parallel in the direction of the bulb. The two long legs  35  are connected to one another via a connecting piece  37 . 
     In an especially preferred embodiment (FIGS. 5 and 6 a - 6   b ), the spring wire piece  31  is shaped somewhat differently. The short leg  34  attached to the base part is bent 180° back toward the approximately equal-length base part  32  and merges with a long leg  35 , which is attached to the short leg via an offset bend  36  such that it extends back again approximately axially parallel in the direction of the bulb. The two long legs  35  are connected to one another via a connecting piece  37 . To assure an especially secure hold of the wire in the recess  14  of the collar  15  (FIG. 2 b ), the central part of the connecting piece  37  is bent backward. This curved piece  38  is located approximately parallel to the plane of the short leg. 
     To further stabilize the spring wire piece  31  and additionally to gain a larger area for contact pressure, a spring sheet metal strip  39  is located between the two short legs  34 , in their own plane. The ends  40  of the spring sheet metal strip are bent over around the short legs  34 .