GB1594901A

GB1594901A - Low pressure mercury vapour discharge lamp

Info

Publication number: GB1594901A
Application number: GB49678A
Authority: GB
Original assignee: Philips Gloeilampenfabrieken NV
Current assignee: Koninklijke Philips NV
Priority date: 1977-01-10
Filing date: 1978-01-06
Publication date: 1981-08-05
Also published as: BE862761A; DE2758664A1; NL7700159A; FR2377093A1; JPS5387589A; FR2377093B3; CA1102389A

Description

(54) LOW PRESSURE MERCURY VAPOUR DISCHARGE LAMP (71) We, N.V. PHILIP'S GLOEILAMPEN FABRIEKEN, a limited liability Company, organised and established under the laws of the Kingdom of the Netherlands, of Emmasingel 29, Eindhoven, the Netherlands, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention relates to a low-pressure mercury vapour discharge lamp having a respective electrode disposed at each end of a tubular discharge vessel and an electricallyconducting strip fastened to the outer surface of the wall of the discharge vessel by means of a bonding material, which strip extends near to both the electrodes.

United Kingdom Patent Specification 592,246 discloses a low-pressure electric discharge lamp having an inert gas filling and of the kind including a longitudinal envelope containing a thermionically activated electrode at each end, and a conductor in the form of a wire strip or foil not connected with either electrode extends along the length of and is cemented to the exterior of the envelope, for example by means of a cement composed of a methacrylate plastic in acetone.

United Kingdom Patent Specification 700,851 discloses a tubular fluorescent lamp bearing a conducting strip on the outer surface of the envelope formed by applying to said surface a suspesion of silver powder in a solution of a thermosetting resin in a suitable solvent, and the baking the said surface to evaporate the solvent and convert the resin into a hard abrasion-resistant medium in which the silver powder is dispersed and which is bonded to the said surface.

The invention provides a low-pressure mercury vapour discharge lamp having a respective electrode disposed at each end of a tubular discharge vessel and an electricallyconducting aluminium strip or aluminium wire fastened to the outer surface of the wall of the discharge vessel by means of a thermosetting adhesive, which aluminium strip or aluminium wire extends near to both the electrodes.

A low-pressure mercury vapour discharge lamp according to the invention has the advantage that satisfactory adhesion of the strip to the wall of the discharge vessel is obtained in a very short period of time so that the machine which is used for fastening the aluminium strip (which strip may consist of, for example, an aliminium foil) or aluminium wire is occupied by each lamp for a very short time only. After the layer of thermosetting adhesive has set, the adhesive cannot soften, even at the high temperatures prevailing in a closed luminaire.

An epoxy resin adhesive is preferably used as the thermosetting adhesive. An example of a suitable adhesive is an adhesive consisting of an epoxy resin and a nitrile rubber, in a weight ratio of 4 parts of epoxy resin to one part of nitrile rubber, to which a hardener, for example dicyane diamide and, possibly, an accelerator such as N-benzyldimethylamine, are added. When applying such an adhesive at a temperature of 175"C sufficient hardening is achieved within a few seconds.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawing, of which: Figure 1 shows an embodiment of a lowpressure mercury vapour discharge lamp according to the invention, and Figure 2 shows a cross-section along the line II--II of the lamp of Figure 1.

In Figure 1 reference I indicates a tubular low-pressure mercury vapour discharge lamp having a power of 40 W. Disposed at each of the ends of the discharge vessel there is a respective circular aluminium sleeve 2 provided with a plate 2a of an electrically insulating material in which two current supply poles 3 and 4 for the electrode are located. The outer surface of the wall of the discharge vessel is provided with an electrically-conducting aluminium strip 5 which extends to near both electrodes and which is fastened to the glass wall of the discharge vessel by means of an epoxy resin adhesive.

By means of an ultrasonically-welded joint, one end 7 of this strip is electrically connected to the aluminium sleeve 2, the latter being electrically connected to supply pole 3 of one electrode via two silver layer 6a applied on the insulating plate 2a and a graphite resistive layer 6b therebetween having a value of approximately 1 MII. At this resistance value the lamp is electrically safe to touch when operating. The aluminium strip is 2 mm wide and 0.1 mm thick. As shown in Figure 2, the inner wall of the discharge vessel is provided with a luminescent layer 8 consisting of calcium halophosphate activated by manganese and antimony.

The aluminium strip 5 is fastened to the outer surface of the glass wall 1 of the lamp by a thermosetting epoxy resin adhesive layer 9 which is disposed between the strip and the lamp wall and is 50 ijm thick.

WHAT WE CLAIM IS: 1. A low-pressure mercury vapour discharge lamp having a respective electrode disposed at each end of a tubular discharge vessel and an electrically conducting aluminium strip or aluminium wire fastened to the outer surface of the wall of the discharge vessel by means of a thermosetting adhesive, which aluminium strip or aluminium wire extends near to both the electrodes.

2. A low-pressure mercury vapour discharge lamp as claimed in Claim 1, wherein the thermosetting adhesive is epoxy resin adhesive.

3. A low-pressure mercury vapour discharge lamp substantially as herein described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. insulating material in which two current supply poles 3 and 4 for the electrode are located. The outer surface of the wall of the discharge vessel is provided with an electrically-conducting aluminium strip 5 which extends to near both electrodes and which is fastened to the glass wall of the discharge vessel by means of an epoxy resin adhesive. By means of an ultrasonically-welded joint, one end 7 of this strip is electrically connected to the aluminium sleeve 2, the latter being electrically connected to supply pole 3 of one electrode via two silver layer 6a applied on the insulating plate 2a and a graphite resistive layer 6b therebetween having a value of approximately 1 MII. At this resistance value the lamp is electrically safe to touch when operating. The aluminium strip is 2 mm wide and 0.1 mm thick. As shown in Figure 2, the inner wall of the discharge vessel is provided with a luminescent layer 8 consisting of calcium halophosphate activated by manganese and antimony. The aluminium strip 5 is fastened to the outer surface of the glass wall 1 of the lamp by a thermosetting epoxy resin adhesive layer 9 which is disposed between the strip and the lamp wall and is 50 ijm thick. WHAT WE CLAIM IS:

1. A low-pressure mercury vapour discharge lamp having a respective electrode disposed at each end of a tubular discharge vessel and an electrically conducting aluminium strip or aluminium wire fastened to the outer surface of the wall of the discharge vessel by means of a thermosetting adhesive, which aluminium strip or aluminium wire extends near to both the electrodes.