Patent Publication Number: US-6340310-B2

Title: Lamp holder

Description:
FIELD OF THE INVENTION 
     Our present invention relates to a lamp holder and, more particularly, to a lamp holder specific to pin-based lamps, for example, compact fluorescent lamps with G 23, G 24 or 2G 11 type sockets and halogen lamps with G 12 or PG 12 type sockets and generally comprised of a housing of electrically insulating material having usually two contact springs whose bent shoulders engage detent recesses or projections on the lamp base so as to provide sufficient retaining force on the base and make an electrical connection with the pin thereof. 
     BACKGROUND OF THE INVENTION 
     Lamp holders of this type serve on the one hand to make electrical connection between the conductors within the lamp and the electric current network supplying the lamp and, on the other hand, to retain the lamp mechanically in the holder. The lamps with which the invention is concerned are primarily those lamps which have detent formations in the lamp base, behind which the shoulder of the contact spring can engage, and contacts which are likewise engageable with the contact spring so as to provide the electrical connections. 
     Lamp holders of this type must have at least one contact spring for retaining the lamp base in position or to secure the lamp base against falling out of the lamp. 
     In a conventional lamp holder for the aforedescribed lamps and which represents the starting point for the present invention and over which the invention is an improvement, the contact spring is bent from a flat strip and has a hairpin shape with two shanks connected together through approximately a 180° bend. The U-shaped member thus has a bight between a shank formed with the shoulder and constituting the base-retaining member and contact shank, and a bracing shank which resiliently engages a wall of the holder housing and urges the first-mentioned shank toward the lamp base. 
     This second shank, which may be referred to as a bracing shank, has an indexing formation formed therefrom and projecting outwardly to engage a formation on the housing behind which this indexing formation can lock. The contact spring is inserted with its U-shaped body into a pocket in the lamp housing in the same direction as the lamp is inserted and, when that contact spring is fully inserted, its detent engages behind the formation of the housing in a snap fit, thereby retaining the contact spring against tractive forces tending to pull it out of the housing. The detent can lie against the wall of the pocket inwardly of the projection and the shoulder on the lamp-retaining shank projects into the path of the lamp base to come into engagement with the latter, whereby that shoulder can be cammed outwardly by the base and spring behind the seat formed in the base for engagement thereof in the lamp holder. 
     Usually the lamp holder has two such pockets, each with a respective contact spring and the contact springs are disposed opposite one another to engage opposite sides of the lamp base. Of course it is also possible to use a single contact spring to retain the lamp base against a fixed abutment on the housing opposite that contact spring. 
     Lamp holders of the aforedescribed type have been found to be highly successful in practice. 
     However, it is always desirable to reduce the amount of material in such devices, to limit the work which goes into producing the unit and, of course, to limit the cost while maintaining the effectiveness of the lamp holder. 
     OBJECTS OF THE INVENTION 
     It is therefore the principal object of the present invention to provide an improved lamp holder, especially for the types of lamps mentioned earlier, whereby the contact spring can be simplified without reduction in its effectiveness and thus a considerable saving of material can be accomplished especially in the case of mass-produced lamp holders. 
     Another object of the invention is to provide an improved lamp holder which utilizes a simplified contact spring and which is therefore more desirable than earlier lamp holders for the same types of lamps. 
     Another object of this invention is to optimize the utilization of material in the fabrication of lamp holders. 
     SUMMARY OF THE INVENTION 
     These objects and others which will become apparent hereinafter are attained in a lamp holder configured to receive a base and, for example, conpact fluorescent lamps of types G 23, G 24 or 2G 11 or have halogen lamps of types G 12 or PG 12 and wherein the insulated housing receives at least one contact spring for retaining the lamp base and mechanically retaining the lamp base in the lamp shoulder housing or socket and wherein the shank of the contact spring provided with the shoulder is free from the aforementioned bight and is not connected to another shank bent from the contact spring via a bight, but rather the bracing shank is formed out of the shoulder forming the lamp-retaining shank and is provided directly with the indexing formation or lug. In other words the lamp-retaining shank has a free end and is generally flat except for a lug which is bent out of that shank between the end thereof and braces against the housing while directly forming the indexing lug, the shoulder and the lug projecting from opposite sides of the same shank. 
     More particularly, the lamp holder comprises: 
     a housing composed of electrically insulating material formed with a cavity opening along a side of the housing; and 
     at least one electrically conductive contact spring received in the housing for engagement with the base of the lamp for mechanical retention of the base and electrical connection therewith, the contact spring being formed from a planar metal strip with a shank having a free end lodged in the housing, a bend at an opposite end of the shank and forming a shoulder engageable with and biased against the base for retaining the base in the housing against tension tending to withdraw the base from the housing, and a barb formed from the shank between the free end and the shoulder and bent from the shank away from a direction in which the shoulder is bent from the shank for bracing against the housing, the barb being formed as a detent lug engaging behind a projection on the housing for retaining the contact spring in the housing. 
     The invention eliminates the need for a separate bracing shank bent from the retaining shank through 180° and the function of that bracing shank is taken over completely by the lug which is bent out of the retaining shank between the ends thereof, this lug serving simultaneously as the indexing element for locking the contact spring in its pocket in the housing. The result is a significant saving of material for the contact springs without requiring a redimensioning of the housing or the balance of the lamp holder. In excess of one-half of the length of the sheet metal strip required for each contact spring is no longer necessary. 
     It has been found to be advantageous to cut out the barb or lug from the retaining shank so that it has a free end turned toward the end of the contact spring provided with the shoulder. 
     The contact spring itself can have a generally flat or planar shank from which the indexing lug or barb can be cut out and bent and which can be provided with the shoulder. The formation of the barb can be such that it itself is different from the lug formed on the bracing shank of the prior art contact spring bent through 180° with respect to the retaining shank in that its free end is turned toward the shoulder rather than toward the free end of the metal strip opposite the shoulder. The barb can be elongated and connected to the retaining shank at an end of the barb turned away from the end of the contact spring provided with the shoulder and the barb can then have a straight portion including an acute angle with the shank and another portion at an obtuse angle of the straight portion and substantially parallel to the shank with the contact spring. Lodged in the housing this other portion can lie flat against the housing and can have an edge engaging the projection for locking the contact spring in the housing. The retaining shank has a portion extending from a junction of the barb with the shank to an end thereof and received in a slit in the housing. 
     With this shape and construction, the requisite bracing and locking function can be achieved without the bent shank extending the retaining shank. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The above and other objects, features, and advantages will become more readily apparent from the following description, reference being made to the accompanying drawing in which: 
     FIG. 1 is a longitudinal section of a lamp holder according to the invention and illustrating a base diagrammatically of a lamp which can be inserted therein; 
     FIG. 2 is a section similar to FIG. 1 showing partial insertion of the lamp base; 
     FIG. 3 is another section similar to FIG. 1 showing the full insertion of the lamp base; 
     FIG. 4 is a side elevational view, greatly enlarged in scale of a contact spring according to the invention; 
     FIG. 5 is a view in the direction of arrow V of the contact spring of FIG. 4; 
     FIG. 6 is a view in the direction of arrow VI of the contact spring of FIG. 4; 
     FIG. 7 is a perspective view of the contact spring of FIGS. 4-6; 
     FIG. 8 is a plan view of the sheet metal strip after it has been ensized for the barb but before the retaining shoulder and the barb are pressed into the sheet metal strip; 
     FIG. 9 is a view similar to FIG. 1 showing a prior art lamp holder; 
     FIG. 10 is a view similar to FIG. 4 but showing the contact spring of the prior art holder; 
     FIG. 11 is a perspective view of that contact spring; and 
     FIG. 12 is a view of the sheet metal strip before bending for the contact spring of FIGS.  9 - 11 . 
    
    
     SPECIFIC DESCRIPTION 
     Referring first to FIGS. 9-12 which serve to illustrate the prior art, it can be seen that the lamp holder  10  can comprise a housing  11  on diametrically opposite sides of which, insertion pockets  12  can be provided which are open toward the  10  base of a lamp to be inserted therein and each of which receives a respective contact spring  13  capable of locking into the pocket. 
     Each contact spring has a retaining shank  14  and a bracing shank  16  connected to the retaining shank by a bight  15 , the two shanks forming a bend at the bight through about 180°. The outer surface  16   a  of the bracing shank  16  presses close to its free end  16   b  on an inner surface  11   a  of the housing  11 . In addition, the bracing shank  16  is formed close to its free end with a U-shaped cut out  17  (FIG. 12) from which a tongue-like barb  18  can be bent outwardly. The barb  18 , once the contact spring has been inserted into the pocket, can engage in an opening  19  in the housing so that its free end  18   a  can lock against a retaining surface  20  of the housing. The retaining surface  20  may be formed on an inward projection of the housing. 
     The contact spring  13  is then locked in the housing in the cutout  19 . By pressing inwardly against the bracing shank  16 , the barb  18  can be released so that the contact spring can be pulled out but aside from that type of release, the spring  13  cannot be pulled out from its seat in the housing and is securely retained there. 
     The retaining shank  14  of the contact spring has an outwardly bent shoulder  21  to engage a base  25  of a lamp. The retaining shank can be resiliently bent as indicated by the arrows  22  at the axes defined by the bights  15  when the lamp base  25  is snapped into the lamp holder  10  as will be described in connection with FIGS. 1-3. In the final fully inserted position of the lamp base, the shoulders snap behind the surfaces of the lamp base which are to be retained by these shoulders and simultaneously make electrical contact with the lamp. 
     From the foregoing it will be apparent that the contact spring  13  has a number of functional elements including the shoulders  21  on the shanks  14  which grip the base  25  of the lamp and the shank  16  which braces the shank  14  inwardly by itself resting against an outer part of the housing. The U-shaped bight  15  serves to interconnect the bracing shank  16  and the retaining shank  14  and the barb  18  is here on the bracing shank. The contact spring  13  is formed from a planar sheet metal strip  23  of a length L (FIG. 12) and the free edge  18 a of the barb  18  is turned toward the end of the bracing shank and hence the end  23   b  which is opposite the end  23   a  formed with the shoulder  21 . 
     The invention has been illustrated in FIGS. 1-8, and in FIGS. 1-3 a lamp holder  110  with a housing  111  has been shown. A pair of opposite contact springs  113  are provided in pockets  119  of the housing and are differently configured from the contact springs of the prior art embodiment of FIGS. 9-12. 
     In the system of the invention, the contact springs  113  have retaining shanks  114  which can be provided with shoulders  121  bent outwardly on the planar shank that has been described previously but there the barb and the indexing lug are formed directly on the retaining shank  114  and thus are integrated therewith. 
     As best seen in FIGS. 5-8, the contact spring  113  has a planar shank  114  from which an elongated spring tongue  26  is bent having been delimited by a U-shaped cut out  117 . A connecting portion  26   a  near the end  14   b  of the shank turned away from the end provided with the shoulder  121  connects a straight portion  27  at an acute angle with the shank  114 . 
     The free end of the tongue  26  is arcuate at  26   b  and is turned toward the end provided with the shoulder, namely, the end  14   a  of the sheet metal strip  123 . 
     The tongue  26  is so formed that the straight portion  27  forms an obtuse angle with another portion  116  which here constitutes the bracing member of the contact spring. This configuration is clearly visible from FIGS. 4-7. These Figures also show that the bracing member  116  is integrated in the retaining shank  114  and thus that the contact spring  13  has no bight  15  and no separate bracing shank  16  as have been described. The blank for the contact spring  13  has been shown at  123  in FIG.  8  and has a length  1  which is significantly less than the length L and may be only slightly greater than one-half the length L of the blank  23  of FIG.  12 . 
     From FIGS. 1-3, it will be apparent that the housing  11  can have slits  28  open toward the mouth of the housing to receive the end portion  14   b  of the retaining shank  114 . Not shown in FIGS. 1-3 are groove-like guides for laterally guiding the edges  14   c  of the retaining shank  114 . 
     Along the interior of the housing  111 , small detent ribs or projections  29  are provided which are engaged by edges  16   b  bracing the legs  116  of the barbs  116 ,  127  which are pressed out of the cut out  117  of the blanks. The barb has a hole which can be represented at  26  and forms the bracing shank which presses the shank  114  resiliently inwardly. The free edge  16   b  thus fulfills the function of the edge  18   a  of the prior art contact spring. 
     When the base  25  is inserted in the direction of arrow A, (FIG.  1 ), the shoulders  21  are cammed outwardly and then snapped behind the ribs  24  on the base  25  (compare FIGS.  2  and  3 ).