Patent Publication Number: US-7221098-B2

Title: Electric lamp with outer bulb and associated support body

Description:
TECHNICAL FIELD 
   Reference is made to application with docket no. 2003P08148DE filed in parallel, which provides a more detailed description of processes for producing a lamp with a getter strip. 
   The invention relates to an electric lamp with outer bulb and with an inner vessel, in particular a discharge vessel, arranged therein, a getter material being held on a support body inside the outer bulb. It deals in particular with discharge lamps, such as metal halide lamps, but also with incandescent halogen lamps. 
   BACKGROUND ART 
   U.S. Pat. No. 5,825,127 has disclosed a process for producing a cap strip for discharge lamps, in which the cap strip is a support strip comprising a material which is to be introduced into the lamp, in particular mercury and/or getter material as a coating. The only application area envisaged for cap strips of this type in that document is as the discharge vessel of a low-pressure mercury lamp. In this case, the cap strip is often secured in the vicinity of an electrode, cf. in this respect also U.S. Pat. No. 6,043,603. A support strip with getter is also referred to as a getter strip. 
   An example of an incandescent halogen lamp with a getter in the outer bulb is to be found in CA-A 1,310,058. 
   Getters are usually used on a disk as a base in the outer bulbs of high-pressure discharge lamps in order to absorb impurities. For example, U.S. Pat. No. 5,327,042 uses a Zr getter on an iron sheet base which is securely welded to the frame. In the case of discharge vessels which are closed on two sides in an outer bulb which is closed on two sides, getters are usually secured in the pinch of the outer bulb using a piece of wire or at the outer supply conductor or at a sheet-metal shell placed around the pinch of the discharge vessel, cf. in this respect Technisch wissenschaftliche Abhandlungen der OSRAM-Gesellschaft, Vol. 12, Springer-Verlag, Berlin 1986, pp. 11 to 14. 
   DISCLOSURE OF THE INVENTION 
   It is an object of the present invention to provide an electric lamp with outer bulb and with an inner vessel, in particular a discharge vessel, arranged therein, a getter material being held on a support body inside the outer bulb which lamp allows simple, inexpensive and space-saving securing of a getter in the outer bulb. A further object is to provide a support body which is particularly well adapted and in particular is especially suited for this purpose. 
   This object is achieved by the feature that the support body is a support strip to which the getter material is applied, the support strip being curved in such a way that it is automatically held in the outer bulb without the need for any auxiliary means. Particularly advantageous configurations are to be found in the dependent claims. 
   The electric lamp according to the invention has an outer bulb and an inner vessel which is arranged therein and is closed off in a vacuum-tight manner, generally a discharge vessel. It is usually held in the outer bulb by means of a frame. However, the lamp may also be an incandescent halogen lamp with an outer bulb. A getter material is held on a support body in the outer bulb, the support body being a support strip to which the getter material is applied as a layer, as is known per se from U.S. Pat. No. 5,825,127. According to the invention, however, the support strip itself is used directly as a holding mechanism, with the support strip being bent in such a way that it is automatically held in the outer bulb without the need for any auxiliary means. 
   The invention may be realized in various ways; in one embodiment, the support strip consists of flexible material. In this case, a simple holding mechanism can be produced by the discharge vessel having at least one pinch, with the support strip being wrapped around at least part of the pinch. If the inner vessel, which is generally a discharge vessel, has at least one fused seal, the support strip is wrapped around at least part of the fused seal. 
   In a second embodiment, the support strip consists of elastic, resilient material, in particular of spring steel. With this condition, it is possible for the support strip to be held on the inner surface of the outer bulb by spring forces alone. 
   Reliable holding is achieved if the support strip is clamped into notches in the inner surface of the outer bulb. 
   One alternative is for the support strip to be bent in such a way that it has at least three bearing points against the inner surface of the outer bulb. 
   A further embodiment requires the support strip to be perforated and to be secured to the discharge vessel in a clamping fashion by bending at the perforated locations. In this case, of course, the support strip may additionally be resilient or at least flexible. 
   Particularly secure holding of the support strip in the outer bulb is achieved by virtue of the outer bulb being provided with a bulge which assists with secure holding of the support strip. 
   A particularly preferred embodiment, in which the advantages of the novel concept manifest themselves particularly clearly, is an arrangement in which the discharge vessel is closed off by sealing parts at opposite ends, with the outer bulb only partially surrounding the discharge vessel and ending in the region of the sealing parts at the latest. 
   One typical application is metal halide lamps and incandescent halogen lamps. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is to be explained in more detail below with reference to a plurality of exemplary embodiments, in which: 
       FIG. 1  shows a side view, in section, of a metal halide lamp; 
       FIG. 2  shows a production process, in highly diagrammatic form, for the lamp shown in  FIG. 1 ; 
       FIG. 3  shows a metal halide lamp in cross section with support strip; 
       FIGS. 4 to 9  show further exemplary embodiments for lamps with support strip in cross section; 
       FIG. 10  shows a plan view of an exemplary embodiment of a perforated support strip. 
   

   BEST MODE FOR CARRYING OUT THE INVENTION 
     FIG. 1  shows a side view of a metal halide lamp  1  which is pinched on two sides. The discharge vessel  2 , which is designed as a barrel-like body made from quartz glass, encloses two electrodes  3  as well as a metal halide fill. The bulb ends are sealed by pinches  4  in which foils  5  are embedded. The foils are connected to external supply conductors  6 . The external supply conductor  6  is guided inside a tubular sleeve  7  and ends in a bush  8  of an integral cap part  9 . The cap is produced as a single part from steel and also comprises a circular disk  10  as contact element and barb  11  as centering and holding means. The part of the discharge vessel which bulges out is surrounded by an outer bulb  12  which is rolled on ( 13 ) in the region of the transition between the pinch  4  and the sleeve  7 . The outer bulb  12  has an encircling indentation  14 , so that an elastic support strip  15  made from iron, in particular nickel-plated, or steel is spread apart against the inner surface of the outer bulb without being able to slip laterally. The support strip contains getter materials, such as Zr, Fe, V, Co, which are used to absorb various substances, such as oxygen, hydrogen or the like. The outer bulb may be filled with nitrogen, another inert gas or vacuum. 
   One possible form of production is described, for example, in US 2002/063 529, US 2002/067 115 or U.S. Pat. No. 5,128,589. A variant with a complete outer bulb is indicated, for example, in CA 2 042 143. The concept of the invention can be used for all these designs. 
   A further production method is described below with reference to  FIG. 2   a : first of all, the discharge vessel  2  is completed from a cylindrical tube by means of a forming roll and if appropriate pinching jaws, which in each case fix an electrode system which has been introduced into the still-open tube, for example by pinching, until the stage at which it has been provided with a seal (pinch  4  or fuse seal) at both ends. At the same time, integrally attached, sleeve-like extension parts  7  remain in place at the seals. While a first extension part  7   a  is being closed up by the end  16   a , which is initially still open, of the extension part being dropped onto a cap part  17  which has been introduced, a pumping hole  18  remains open at the second extension part  7   b . Moreover, the open end  16   b  is not initially treated. In parallel, the cylindrical outer bulb  12  is pretreated until an encircling indentation  14  laterally fixes a support strip clamped next to it in the outer bulb  12 . The ends of the outer bulb are then rolled onto the extension part  7  on both sides by means of prior heating by flames (arrow P 1 ), specifically in such a way that the fixing at the end  16   b  of the second extension part  7   b  takes place outside the still-open pumping hole  18 . At the height of the pumping hole  18 , although the outer bulb  12  is rolled in down to a fraction of its original diameter, it is not yet rolled in to such an extent that it bears against the extension part  7   b  (arrow P 2 ). At the still-open end  16   b  of the second extension part  7   b , this arrangement is connected via a feedline  38  to a pumping and filling system  39 , in particular by a pumping rubber  40  being fitted to the end of the extension part. The atmosphere in the outer bulb can then be evacuated. The pumping path is indicated as arrow P 3 . Then, the outer bulb  12  can be supplied with a substantially inert atmosphere via this pumping path or a vacuum can be maintained. In the next step, the pumping hole  18  is closed up, either by being closed by rolling, being melted shut by means of a laser, or simply by material automatically dropping onto it after heating under the application of reduced pressure. Then, the end  16   b  of the second extension part is also “shrunk on”. The getter strip  15  may, if necessary for the getter used, subsequently be activated through the outer bulb  12  by means of a laser. 
   Instead of an indentation  15  as an inwardly facing bulge as the lateral boundary, it is also possible to use an outwardly facing bulge ( 52 ) in which the support strip is guided on account of the two-part lateral delimitation, cf.  FIG. 2   b.    
     FIG. 3  shows the principle of a further way of securing the support strip. In this case, the support strip  20  is secured directly to the H-shaped pinch  21  (shown in cross section) by being bent in such a way that two contact sections  22  thereof touch the two wide sides  23  of the pinch  21  in a clamping manner, whereas a central section  24 , located between them, of the support strip surrounds a first narrow side  25  at a distance therefrom. The free ends  26  of the support strip protrude towards the second narrow side  27  at the pinch. 
   A similar concept can also be used for a lamp with a fused seal  28 .  FIG. 4  shows a cylindrical fused seal  28  in section. The support strip  29  with getter surrounds the fused seal  28  virtually completely, specifically it surrounds at least three quarters of its circumference, bearing against it at at least three points. The free ends  30  of the support strip are bent back through approximately 330° and are also angled off through approximately 90° at the direct end, with these free end pieces acting as a fitting aid. 
   Another concept is shown in  FIG. 5 . In this case, the support strip  31  is not secured to the pinch  21  (or fused seal), but rather to the inner surface  32  of the outer bulb, by virtue of the support strip being formed from spring steel or nickel-plated iron approximately as an isosceles triangle with rounded corners  33  and an open base  34 . The rounded corners form the three contact points with respect to the outer bulb. To be held securely, it is advantageous if the three contact points span slightly more than half the circumference of the outer bulb, in particular approximately 55 to 75%. The temperature to which the support strip is exposed, on account of its proximity to the discharge vessel, is in this case relatively high, and consequently this configuration is eminently suitable for getter materials which require a high temperature in order to be effective. This concept is also eminently suitable for fused seals, since fused seals take up less space than pinches. 
   A second variant shown in  FIG. 6  is designed for getters which require a relatively low temperature to provide an optimum efficiency. In this case, the support strip  35  is nestled significantly more closely to the inner surface  32  of the outer bulb. For this purpose, the support strip  35  is bent approximately in a C shape, so that it acquires a further distance from the pinch  21  of the discharge vessel. 
     FIG. 7  shows a further embodiment. In this case, the support strip  36  is clamped between two slots  37  at the inner surface  32  of the outer bulb, so that it is curved in a roof shape. The two slots  37  are arranged slightly eccentrically with respect to an imaginary parallel diameter D, with this connecting straight line V between the slots being offset with respect to the parallel diameter D to such an extent that it lies approximately at the height of the ends of the narrow sides of the H-shaped pinch  21 . The spring stress is preferably selected in such a way that the support strip  36  has a length of approximately 120 to 160% of the length of the connecting straight lines V between the slots  37 . 
   A further embodiment uses a perforated support strip  41  for securing to the discharge vessel  42 , so that the bends in the support strip can be better matched to the shape of the H-shaped pinch  21 .  FIG. 8  shows a support strip  41  which, in a similar manner to in  FIG. 3 , is clamped securely to two wide sides  43  of the pinch, with a central section  44  surrounding a narrow side  45 . Unlike in  FIG. 3 , however, suitable perforation of the support strip allows the central section  44  of the support strip to run parallel to the narrow side  45  and then to be bent off at right angles toward the wide sides. There, contact with the wide sides is effected in each case by means of an end section  46  which is V-shaped in form. In this way, the space taken up by the support strip is considerably reduced. This embodiment is particularly suitable for getters with a high working temperature and for lamps with a short distance between the outer bulb and the discharge vessel. 
     FIG. 9  shows an exemplary embodiment of a perforated support strip  47  which is secured to a fused seal  28 . Compared to  FIG. 4 , the perforation allows a shorter support strip  47  to be used. The support strip is wrapped around the fused seal, which is cylindrical in cross section, over approximately 70 to 90% of its circumference, with five lines of perforations allowing sharp ends  48  to be made in the support strip. This makes the holding more reliable and more tightly fitting. There is no need for an extension as a fitting aid, as in  FIG. 4 . 
     FIG. 10  diagrammatically depicts a perforated support strip  47 . In the unbent state, it is a metal sheet which has been cut at right angles and to which a getter material  49  has been applied, for example as a centrally running ribbon. In the exemplary embodiment shown (left-hand half), by way of example, five slots  50  have been punched into the support strip as perforation lines. Of course, the perforation may also be configured differently, for example may be formed by rows of stamped holes  51  along a line, as shown in the right-hand half of  FIG. 10 . The number of lines of perforations depends on the number of desired bends. 
   The stamped holes have the advantage that they can be formed over a greater proportion of the width of the metal sheet than the slots. On the other hand, the slots, the length of which is greater than the width of the getter-containing ribbon  49 , have the advantage that it is impossible for any getter material, for example zirconium oxide, to flake off or crumble away when the metal sheet is being bent. 
   Of course, this technique can also be used for discharge vessels which are closed on one side, in particular pinched. This may be accommodated in an outer bulb which is closed on one side. Accordingly, the technique can also be used for a discharge vessel which is closed on two sides in an outer bulb closed on one side.