Abstract:
A lamp socket for multipin lamps with spring-biased contacts for contacting the contact pins of a lamp, and a housing which in the final assembly state at least partially surrounds the lamp base of the lamp. The housing is composed of an upper housing part which supports a device for aligning and securing the lamp, and a bottom hosing part which supports at least indirectly receiving means for the contacts. The spring-biased contacts provided for contacting the various contact pins are arranged in individual electrically insulating and housing-like contact cages which are moveable independently of each other.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a lamp socket or holder for multipin lamps with spring-biased contacts for contacting the contact pins of a lamp, and a housing which in the final assembly state at least partially surrounds the lamp base of the lamp, wherein the housing is composed of an upper housing part which supports a device for aligning and securing the lamp, and a bottom hosing part which supports at least indirectly receiving means for the contacts. 
     2. Description of the Related Art 
     Lamp sockets of the above-described type are frequently used for securing and electrically contacting lamps in various lighting devices. In addition to the lamp and socket, these lighting devices frequently also include reflecting and/or refracting optical systems of various complexity which are optimized for the respective purpose of use. It is of particular importance in this connection that the actual incandescent filament is positioned in a well defined spatial relationship relative to the surrounding optical system. In a predominant number of cases, a manual adjustment of the incandescent filament and/or the optical system adapted to each individual case is not possible. Rather, most manufacturers construct the lamps in such a way that the incandescent filament has a precisely specified alignment relative to a contact surface or contact line at the lamp base. Consequently, the sockets which are usually fixed relative to the optical lighting system have in most cases a corresponding reference surface whose purpose it is to ensure an automatic alignment of the lamp, for example, by biasing the lamp base relative to the reference surface by a spring. 
     However, a more fundamental purpose of the lamp socket is to provide a secure electrical contact of the contact pins which must be ensured even at high temperatures and after frequent replacements of the lamp. 
     In order to meet this object, various solutions have been proposed. Sockets are known in the art which, among other features, include a ceramic bottom housing part which is provided with recesses for inserting the contact pins. One of these recesses is usually tapered in the shape of a prism, wherein a spring-biased contact plate is arranged opposite the prism-shaped taper so that the inserted contact pin is pressed by the contact plate into the prism-shaped groove and the contact pin is secured relative to the bottom housing part as a result. Additional contact pins are secured in a similar manner, wherein, however, manufacturing tolerances must frequently be taken into consideration by providing the recesses with the shape of oblong holes. 
     However, this results in the decisive disadvantage that two pairs of reference are defined, i.e., the lamp base and the upper housing part, on the one hand, and the contact pin and the upper housing part, on the other hand, wherein the relative alignment of the contact surface or line at the lamp base relative to those at the contact pins is not specified and is usually subject to significant manufacturing tolerances. At which pair of reference the alignment actually takes place depends essentially on the dimensioning of the spring forces which, however, may also be subject to variations due to temperature changes. 
     Another disadvantage is the fact that, when the alignment takes place at the contact surface provided by the lamp manufacturer, contacting of the contact pins can only be optimized in exceptional cases. Especially in the case of higher temperatures, this results in contacting problems which significantly reduces the reliability of the entire lighting device. 
     A contacting device which is supposed to eliminate this disadvantage is disclosed in DE 295 19 948.2. In that case, the contact is provided by two shaped parts which engage in each other in an articulated manner, wherein the shaped parts form together a receiving means for a contact pin on one side of the point of engagement between the shaped parts, and wherein the shaped parts include a helical spring on the other side of the point of engagement, and wherein the helical spring produces a resilient force acting against the expansion of the receiving means as a result of the insertion of the contact pin. The entire contact unit is movably mounted in a plane extending perpendicularly of the desired position of the contact pins, so that the position of the contacts can adapt to the respective position of the contact pins. No force acts on the lamp base proper, so that a defined alignment at the contact surface of the lamp base and the corresponding reference surface of the lamp socket becomes possible. However, this device has the disadvantage that the contacts are complicated and expensive to manufacture, and that there is no possibility for an adjustment to contact pins which are in an inclined position. Moreover, the contacts must be manufactured of an electrically conductive material, which makes it necessary that the contacts are embedded in a ceramic socket base; because of the moveable support, the socket base must be constructed of two parts which results in additional costs. 
     In accordance with another solution known in the art, individual contacts are provided for each contact pin, wherein the contacts have a cylindrical shape which corresponds to the contact pins. The contacts are manufactured from a base plate with several tongues, wherein the tongues are bent perpendicularly relative to the base plate and are at their upper ends connected to a spring ring. This results in a cup-shaped structure which is inserted in a ceramic housing base, wherein a contact pin each is placed in the cup-shaped structure. However, this solution has significant disadvantages. The diameter of the opening of the contact cup can be expanded elastically only to a minimal extent, so that the sometimes significant tolerances in the diameters of the contact pins can be compensated only insufficiently. Consequently, particularly in the case of high temperatures, incorrect contacting frequently occurs. Moreover, only a restricted mobility of the contact cups relative to the ceramic socket base can be realized because the contact pin must be inserted very precisely into the opening of the cup in order to ensure that the contact pin does not slide next to the cup and destroys it. This results in an insufficient positional alignment of the contacts relative to the contact pins. Finally, it is also in this solution absolutely necessary to provide an electrically insulating housing base with guide means for the contact pins, so that particularly inclined positions of the contact pins can be compensated only insufficiently. 
     SUMMARY OF THE INVENTION 
     Therefore, it is the primary object of the present invention to provide a socket of the above-described type which, on the one hand, ensures a reliable contacting of the contact pins and, on the other hand, facilitates an alignment of the lamp exclusively at the contact surface provided at the lamp base, wherein the inexpensive manufacture is of particular significance. Another object, which is of less significance and concerns especially the aspect of the inexpensive manufacture, is to provide a modular construction of the contacts which facilitates the use in sockets of different shapes and/or materials and which especially also provides a greater freedom of the design of the socket. 
     In accordance with the present invention, the spring-biased contacts provided for contacting the various contact pins are arranged in individual electrically insulating and housing-like contact cages which are moveable independently of each other. 
     As a result of the configuration according to the present invention, a single spring-biased contact is provided for each contact pin of the lamp to be contacted. The contact is arranged in an electrically insulated, preferably ceramic, contact cage. This contact cage is essentially freely moveable relative to all other units of the socket which includes translatory movements along all spatial axes and partial rotations about the axes. Because of the positional adjustment of the contact cages relative to the contact pins, the contact pins are contacted by spring-biased contact plates always parallel to the contact pins which ensures an optimum contacting. Preferably, each contact pin is inserted into a prism-shaped recess of the contact cage, so that the secure support of the contact cage and the contact of the contact pin are further improved. The contact plates are preferably pressed against the contact pin by a helical spring. This results in a spring range which is especially long, so that a safe contacting is also ensured in the case of higher temperatures. 
     Another advantage of the socket according to the present invention is the fact that it is possible to use a lower housing part of particularly simple construction. Since the insulation between the contacts and relative to the housing is already for the most part ensured by the electrically insulating contact cages, it is only necessary to provide in the lower housing part a sufficiently large space for receiving all contact cages. A particular spatial and/or electrical separation is not required. In particular, this results in the possibility of manufacturing the lower housing part at least partially of metal materials which may provide advantages with respect to carrying of heat and the design of the socket. 
     The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, specific objects attained by its use, reference should be had to the descriptive matter in which there are described preferred embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     In the drawing: 
     FIG. 1 is a perspective view of the lamp socket according to the present invention; 
     FIG. 2 is a perspective view of the upper housing part of the socket of FIG. 1; 
     FIG. 3 is a perspective view of a spring element for pressing the contact surface of the lamp base against the reference surface of the upper housing part; 
     FIG. 4 is a perspective view of an insulating intermediate layer; 
     FIG. 5 is a perspective view of the lower housing part with contact cages shown next to the lower housing part; 
     FIG. 6 is a perspective view, on a larger scale, of a contact cage with spring-biased contact and lead; 
     FIG. 7 is a front view of a contact plate; 
     FIG. 8 is a side view of a contact plate; 
     FIG. 9 is a side view of a helical spring for resiliently biasing the contact plate of FIGS. 7 and 8, as shown in FIG. 6; 
     FIG. 10 is a front view of a lamp for assembly in the socket according to the present invention; and 
     FIG. 11 is a side view of the lamp of FIG.  10 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the embodiment of the present invention shown in the drawings, the socket  1  is composed of an upper housing part  10  and a ceramic lower housing part  20 . The lower housing part  20  has a space  22  for receiving the contact cages  30 . The upper housing part  10  which is preferably made of nickel-plated sheet steel, is particularly distinguished by the presence of a reference surface, wherein, in the final assembly state, the contact surface  44  of a lamp base  43  of a lamp  40  comes to rest against the reference surface  11 . The lamp  40  to be mounted on the lamp base  43  further includes a glass bulb  41 , an incandescent filament  42  and contact pins  45  protruding from the lamp base. 
     In order to ensure an automatic and secure alignment when the lamp  40  is inserted into the socket  1 , a spring element  14  is provided in the upper housing part  10 ; in the illustrated embodiment, the spring element  14  is a plate spring. The spring element  14  is composed of the actual spring body  141  to which an upper fastening edge  142  and a lower fastening edge  143  are integrally connected. The fastening edges  142 ,  143  at least partially engage behind the upper and lower edges of the upper housing part  10  located opposite the reference surface  11 . In this manner, the spring element  14  is pretensioned. When the lamp  40  is inserted, the contact surface  44  of the lamp base  43  is pressed against the reference surface  11  of the upper housing part  10 , so that the incandescent filament  42  is automatically aligned relative to the optical system of the lighting device. 
     In accordance with a preferred feature, in order to ensure a simpler insertion of the lamp base  43  into the upper housing part  10 , the portions of the upper edges  12  of the upper housing part  10  which are not engaged by the upper fastening edge  142  of the spring element  14  are bent outwardly at an angle. The material of the upper housing part  10 , i.e., nickel-plated sheet steel, is selected for the same reason because this material has particularly smooth surface which facilitates a simple insertion of the lamp socket  43 . In addition, it is possible to very inexpensively manufacture punched and bent components of sheet steel. 
     In accordance with the present invention, the lower housing part  20  has essentially two functions, i.e., supporting the upper housing part  10  and receiving the contact cages  30 . In the embodiment illustrated in the drawings, the lower housing part  20  additionally has the purpose of securing the entire socket  1  in the lighting device. For this purpose, guide means  24  for fastening means are provided in the lower housing part  20 . 
     The contact cages  30  are received in the recess of the lower housing part  20  provided for this purpose. In accordance with the invention, the size of the recess is selected such that the contact cages  30  remain sufficiently moveable and the contact cages  30  can completely adjust their position relative to the contact pins  45 . The lower housing part has additional recesses  23  for receiving the electric leads  38 . 
     FIG. 6 of the drawing shows a contact cage  30  according to the present invention as a detail. The contact cage  30  is manufactured of an electrically insulating material, preferably ceramic material. The contact cage  30  has a recess  31  for receiving a contact pin. The recess can be realized particularly advantageously as a breakthrough. The recess  31  can be divided into two portions. A first portion, which is preferably constructed so as to be unilaterally prism-shaped  32 , serves for actually receiving the contact pin  45 . This first portion is separated from a second portion of the recess  31  by a contact plate  33 . The second portion of the recess  31  provides space for an electric lead  38  connected to the contact plate  33 , preferably by welding  36 , and for a helical spring  35  which is pretensioned and rests against the wall of the recess  31 , on the one hand, and against the contact plate  33 , on the other hand. As a result, when the contact pin  45  is not yet inserted, the contact plate  33  is pressed against a projection  34  serving as a guide means and is held in its position. 
     The first portion of the recess  31  must be dimensioned in such a way that an insertion of the contact pin  45  is possible only in such a manner that the contact plate  33  is displaced against the force of the helical spring  35 . As a result of the prism-like shape of the recess  31 , the entire contact cage  30  can be aligned relative to the contact pin  45  in such a way that the contact plate  33  rests against the contact pin  45  always parallel, i.e., with a maximum contact of its contact surface  331 . The long spring range provided by the helical spring  35  ensures that a sufficient contact pressure is always ensured even at higher temperatures. 
     In order to facilitate an easier insertion of the contact pins  45  into the recess  31  provided for this purpose, the upper edges of the first portion of the recess  31  are preferably bevelled. Also, as illustrated in FIGS. 6 and 8, the upper edge  332  of the contact plate  32  are bent outwardly at an angle. The contact plate  32  is preferably manufactured of a temperature-resistant contact material. The outwardly bent upper edge  332  provides the additional advantage that the helical spring  35  is secured against ejection. In accordance with an advantageous feature, the contact cage has a special recess  37  for allowing the electric lead to extend therethrough. 
     A variety of other configurations of the contact cage  30  are conceivable. For example, the contact cage  30  may be provided with more electrical insulation toward all sides than is the case in the embodiment shown in the drawings. 
     For example, in the embodiment illustrated in the drawings, the electric insulation of the contact plate  33  and the helical spring  35  relative to the upper housing part  10  of metal is realized by the electrically insulating intermediate layer  25  shown in FIG.  4 . It is important that the openings  251  in the intermediate layer  25  are significantly greater than the diameter of the contact pins  45  to be inserted. If this were not the case, the contact pins  45 , for example, when they are in an inclined position, could be held by a component which is rigidly connected to the lower housing part  20 ; this would be contrary to the basic concept of the basic invention, namely the exclusive alignment of the lamp by means of the contact and reference surfaces. 
     The illustrated embodiment includes additional advantageous details which will be discussed below. The upper housing part  10  is provided with fastening legs  13  which, when the socket  1  is mounted, are inserted into corresponding slots  22  of the lower housing part  20 . The slots  22  preferably extend through the entire lower housing part  20  and continue at the bottom side in a recess having a greater width, so that the upper housing part  10  can be secured to the lower housing part  20  by staggering the fastening legs  13  relative to each other. 
     In addition, the outer edges of the contact cages  30  are bevelled, so that the contact cages  30  are prevented from being wedged against each other; this would be harmful to the individual alignment of each contact cage  30  in accordance with the specific location of the corresponding contact pin  45 . 
     Of course, additional modifications of the socket according to the present invention, not shown in the drawing, are possible. Some of the possible variations are described in the following. The upper and lower housing parts  10  and  20  do not necessarily have to be constructed as two parts. A single-piece construction of the housing of metal material is conceivable if, for example, by the use of a cover and a base plate at the contact cages, it is ensured that the current-conducting components are completely insulated. This may be advantageous particularly with respect to carrying of heat. If the housing is constructed of two components, various other geometrical configurations are possible. In particular, the ceramic lower part  20  could be at least partially surrounded by the upper part  10 . Spring elements  14  other than plate springs could be used for aligning the lamp base  43  with its contact surface  44  at the reference surface  11  of the upper housing part  10 . It is especially also conceivable to construct the reference surface  11  as a resilient structure, so that the lamp base  43  is spring-biased and secured from both sides. Moreover, the combination of contact plate  33  and helical spring  35  of the contact cages  30  could be replaced by a contact plate  33  constructed as a plate spring. Also, various possibilities are available for connecting the electric lead  38  to the contact plate  33 . Of course, embodiments of lamps  40  with more than two pins  45  are conceivable, wherein especially the shape and size of the pins  45  can be essentially freely elected. Consequently, the socket  1  illustrated in the drawing is intended only as an example and the invention is not limited to this embodiment. 
     While specific embodiments of the invention have been described in detail to illustrate the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.