Abstract:
The electric discharge lamp comprises a shell ( 1 ) having an axis ( 2 ), which shell accommodates a starter ( 3 ) and pin-shaped contacts ( 4 ) extending in an axial direction. A cover ( 27 ), which is coupled to a discharge vessel ( 20 ), is attached to the shell ( 1 ). Pairs ( 23 ) of current conductors ( 24 ) emanate from the discharge vessel ( 20 ). The conductors ( 24 ) of each pair ( 23 ) are clamped, in a direction transverse to the axis ( 2 ), by first and second ( 6 ) forked contact elements, which are secured in the shell ( 1 ) and are directed towards the cover ( 27 ). The lamp is of a simple construction, which can be readily produced.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an electric discharge lamp comprising: 
     a shell having an axis, which shell accommodates a starter and is provided, on an outside, with electric contacts which are to be connected to a power supply; 
     a hermetically sealed discharge vessel comprising electrodes in end portions, which electrodes are each connected to a pair of current conductors which issue from the relevant end portion to the exterior; 
     a cover which is fixed on the shell in a direction transverse to the axis, which cover is rigidly attached to the discharge vessel, the pairs of current conductors each being connected to the starter and to a respective electric contact. 
     2. Description of Related Art 
     Such a discharge lamp is disclosed in DE-A 33 33 294. 
     The known lamp comprises a shell which accommodates, apart from the starter for igniting the lamp, a ballast to limit the current flowing through the lamp during operation. The contacts of the shell are situated at an Edison-cap, i.e. a screw cap. The shell of the cap serves as a first contact, and a bottom of the screw cap which is isolated from the shell of the cap serves as a second contact. The ballast and the Edison-cap enable the lamp to be directly connected to the electric mains. 
     The discharge vessel and the cover of the known lamp are detachably secured to the shell. For this purpose, the discharge vessel is specially provided with axially directed, rigid pins, which come into contact with the ballast when the cover is placed on the shell. 
     A drawback of the known lamp resides in that the shell comprises a ballast, leading to much assembly work in the manufacture of the lamp and causing the lamp to be bulky. Another drawback of the lamp resides in that special, unusual, rigid pins must be provided at the discharge vessel. Yet another drawback resides in that the discharge vessel with the cover can be detached from the shell, so that arrangements must be made to ensure that all live parts in the shell are inaccessible to the user. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an object of the invention to provide an electric discharge lamp of the type described in the opening paragraph, the construction of which is simple, safe and readily reproducible. 
     In accordance with the invention, this object is achieved in that, for each pair of current conductors, a first and a second forked contact element facing the cover is attached in the shell, in which contact element a respective current conductor is tightly and inextricably fixed so as to extend transversely to the axis, and the contacts at the shell are pin-shaped and extend along the axis. 
     Owing to the pin-shaped contacts, the lamp cannot be directly connected, via a screw socket or bayonet socket, to the electric mains, but instead is applied using an external ballast which, for example, is accommodated in a luminaire. As a result, the construction of the lamp is comparatively simple, and the lamp is not very bulky. 
     In the assembly process of the lamp, the contact elements enable the shell and the cover with the discharge vessel to be united simply by pressing the shell and the cover against each other, and to simultaneously form electric connections, via the contact elements, between the current conductors on the one hand and the electric contacts on the other hand. This also enables the discharge vessel to be secured to the cover before the discharge vessel is electrically connected to the shell. Thermal processes, such as soldering electric connections and, for example, cementing for connecting the shell and the discharge vessel to each other, can thus be avoided in the final step in the manufacture of the lamp. 
     The forked contact elements are known per se as “piercing contacts”. These forked contact elements comprise a metal plate, an edge of which is provided with a slit having a narrowing entry. A metal conductor, for example a wire, may be provided in the entry of the slit so as to extend transversely to the plate, whereafter said conductor is laterally pressed into the slit. The slit and the wire are dimensioned so that the contact element forms grooves in the conductor, resulting in a close and mechanically strong contact. If the connection is inaccessible to tools, the connection generally cannot be interrupted in a non-destructive manner and hence is inextricable. 
     In a favorable embodiment, the starter has current-supply wires, and the first contact elements comprise a forked portion, wherein the current-supply wires are tightly accommodated. This embodiment has the advantage that, for example, soldered joints between the starter and the contact elements are avoided. 
     It is possible that the contact elements were present when the shell was manufactured, as a result of which they are anchored in the shell. Advantageously, however, the shell has seatings and the contact elements are tightly accommodated in a respective seating. This has the advantage, inter alia, that the shell can be manufactured in a simpler mold. 
     Another advantage of said embodiment resides in that the forked portion accommodating the current-supply wires may be directed away from the cover. This has the advantage that if the starter is arranged in the shell prior to the contact elements, the electric connection between the contact elements and the starter is formed at the same time. 
     It is desirable for the lamp to comprise an anti-hum capacitor. In a modification, this capacitor having conducting wires is accommodated in the shell, and the first contact elements comprise a second forked portion facing away from the cover, in which forked portion the conducting wires are tightly accommodated. In the manufacture of this modification, the electric connections of the starter and the capacitor are simultaneously formed when the contact elements are provided. 
     In a favorable embodiment, the second contact elements are integral with the electric contacts. This embodiment has the advantage that making electric connections between the contacts and the second contact elements can be dispensed with. 
     The shell and the cover may be, for example, clamped together. It is attractive, however, if they are permanently interconnected. They may be attached to each other, for example, by local fusion or bonding using an adhesive. In an advantageous embodiment, however, the cover and the shell are secured to each other by means of a click-connection, in particular a concealed, i.e. invisible and inaccessible, click connection. In this case, the shell and the cover are interconnected in an assembly operation, i.e. without using thermal or other processes. 
     The discharge vessel may comprise, for example, a curved tube or various series-connected, curved or straight tubular portions. The discharge vessel may be connected to the cover by means of, for example, a cement or an adhesive, such as a UV-curing adhesive. 
     The contact elements may be made from, for example, phosphor bronze or stainless steel. The shell and the cover may be manufactured from a synthetic resin, for example a thermoplastic, such as polybutylene terephtalate. 
     These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. 
    
    
     BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a plan view of the lamp; 
     FIG. 2 is an axial, cross-sectional view taken on the line II—II in FIG. 1; 
     FIG. 3 is an axial, cross-sectional view taken on the line III—III in FIG. 1; 
     FIG. 4 is a view of the empty shell according to IV in FIG. 2; 
     FIG. 5 is a plan view of a first contact element; 
     FIG. 6 is a view of the first contact element according to VI in FIG. 5; 
     FIG. 7 is a view of the first contact element according to VII in FIG. 6; 
     FIG. 8 is a perspective view of a detail shown in FIG. 4 after mounting steps; 
     FIG. 9 is a perspective view of the inside of the cover shown in FIG. 1, and 
     FIG. 10 diagrammatically shows the wiring of the lamp with the contact elements. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The figs. are purely diagrammatic and not drawn to scale. Particularly for clarity, some dimensions are exaggerated strongly. In the figs., like reference numerals refer to like parts whenever possible. 
     FIG. 1 shows the discharge vessel  20  of the lamp, which discharge vessel is secured in the cover  27 . In the embodiment shown, the discharge vessel  20  has four straight, tubular portions  29 , which are connected in series by bridges  30  (cf. FIGS.  2  and  3 ). The lamp is a low-pressure mercury vapor fluorescent lamp. 
     In FIG.  2  and FIG. 3, the electric discharge lamp comprises a shell  1  with an axis  2 . The shell  1  accommodates a starter  3 . The shell  1  is provided, on an outside, with electric contacts  4 , which are to be connected to a power supply. The hermetically sealed discharge vessel  20  comprises, in end portions  21 , see FIG. 2, electrodes  22  which are each connected to a pair  23  of current conductors  24 , which issue from the relevant end portion  21  to the exterior. A cover  27  is secured on the shell  1 , in a direction transverse to the axis  2 . The cover  27  is rigidly attached to the discharge vessel  20 , in this embodiment by means of cement  31 . The discharge vessel  20  is covered with fluorescent powder  33 . The pairs  23  of current conductors  24  are each connected to the starter  3  and to a respective electric contact  4 , also see FIG.  8 . 
     For each pair  23  of current conductors  24 , a first forked contact element  5 , see FIG. 3, and a second forked contact element  6  directed towards the cover  27 , see FIG. 2, are secured in the shell  1 , in which contact elements, a respective current conductor  24  is tightly and inextricably fixed transverse to the axis  2 . The contacts  4  at the shell  1  are pin-shaped and extend along the axis  2 . In this embodiment, the shell  1  and the cover  27  are made from polybutylene terephtalate, and the contact elements  5 ,  6  are made from phosphor bronze. 
     FIG. 2 shows that the second contact elements  6 , in the embodiment shown, are integral with the electric contacts  4 . Apart from the starter  3 , the shell  1  accommodates an anti-hum capacitor  10 , which electrically shunts the starter  3 . 
     As shown in FIGS. 2 and 3, the shell  1  includes seatings  9 . The contact elements  5 ,  6  are tightly accommodated in a respective seating  9 . 
     FIG. 4 shows, in the interior view of the shell  1 , right-angled seatings  9  for the first contact elements  5  and straight seatings  9  for the second contact elements  6 . The right-angled seatings  9  are used to tightly accommodate the first contact elements  5  of FIGS. 5,  6  and  7 . 
     FIG. 5 shows the first contact elements  5  in the position from which it can be accommodated in the seating  9  at the top of FIG.  4 . In this position, the first, forked contact element  5 , see FIGS. 6 and 7, is directed towards the cover  27 , see FIGS. 2 and 3. The first contact element includes a forked portion  8 , see FIG. 6, which is directed away from the cover  27 . FIG. 6 also shows a second forked portion  27 , which is also directed away from the cover  27 . 
     The starter  3  is provided with current-supply wires  7 , see FIGS. 2,  3  and  8 , which are tightly accommodated in the relevant forked portion  8 . 
     Shell  1  also accommodates a capacitor  10 , see FIGS. 2 and 3, which has conducting wires  11 , which wires  11  are tightly accommodated in the second forked portion  12 , which faces away from the cover  27 , of the first contact elements  5 . 
     The shell  1  and the cover  27  are inextricably connected to each other, in FIG. 3, by a click connection  18 ,  28 . 
     In FIG. 8, the starter  3  is provided in the shell  1 , a current-supply wire  7  of said starter being visible. Also a conducting wire  11  of the capacitor  10  is visible, which capacitor is shown in FIGS. 2 and 3. The current-supply wire  7  and the conducting wire  11  are each arranged in a recess  13  of the seating  9 , and extend transversely across the seating. Subsequently, the first contact element  5  is provided in the seating  9 , whereby the forked portion  8  facing away from the cover, referenced  27  in FIGS. 2 and 3, and the second forked portion  12  facing away from the cover tightly accommodate, respectively, the current supply wire  7  and the conducting wire  11 , in a direction transverse to the axis  2 . The first forked contact element  5  is directed towards the cover and ready to tightly accommodate a current conductor  24  of the discharge vessel  20 , see FIGS. 2 and 3, in such a way that said current conductor  24  extends transversely to the axis  2 . If the other first contact element  5  is provided correspondingly, and if the second contact elements  6  are provided, the shell  1  with its contents is ready to be united with the cover  27  and the discharge vessel  20 . The contents of the shell  1  is provided entirely by assembly operations, i.e. without thermal or other processes. 
     In FIG. 9, the cover  27  has openings  32  through which the discharge vessel  20 , see FIGS. 2 and 3, can project. If the discharge vessel  20  is secured in the cover  27 , the current conductors  24  can each be arranged in a groove  35  of a first counterseating  25 , wherein a first contact element  5  can be accommodated, for example, with clearance, and in a groove  36  of a second counterseating  26  for a second contact element  6 , so as to extend transversely to the axis  2 . The cover  27  and everything attached thereto is ready to be united with the shell  1 , so as to form the finished lamp shown in FIG.  1 . For this purpose, the cover  27  is pressed onto the shell  1 , as a result of which the current conductors  24  are rigidly fixed in position by the contact elements  5 ,  6  in order to connect them inextricably to each other, and, in the embodiment shown, the shell  1  and the cover  27  are mechanically connected to each other by the click connection  18 ,  28 , as shown in FIG.  3 . 
     In FIG. 10, corresponding parts bear the same reference numerals as in the preceding figs. A ballast B is accommodated in an external circuit to which the electric lamp is connected by means of the pin-shaped contacts  4 . In the lamp, one current conductor of each pair  23  of current conductors  24  is tightly accommodated in a second contact element  6 , and the other current conductor is tightly accommodated in a first contact element  5 . The starter  3  has current-supply wires  7 , which are tightly accommodated in a respective first contact element  5 . Also the capacitor  10  has conducting wires  11 , which are tightly accommodated in a respective first contact element  5 . If the lamp is energized, a glow discharge occurs in the starter  3  and current passes through the electrodes  22 . Said electrodes  22  heat up, as a result of which they start emitting more readily. The starter  3  comprises a bimetal electrode, which also heats up and bends in a direction away from the second electrode, causing the glow discharge to be extinguished. A voltage pulse is then applied across the discharge vessel  20 , which is capable of igniting the lamp. The voltage across the discharge vessel  20  of a burning lamp is too low to bring about another glow discharge in the starter  3  after the bimetal electrode has cooled. 
     It will be obvious that, within the scope of the invention, many variations are possible to those skilled in the art. The scope of protection of the invention is not limited to the examples given herein. The invention is embodied in each novel characteristic and each combination of characteristics. Reference numerals in the claims do not limit the scope of protection thereof. The use of the verb “to comprise” 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.