GB1572338A

GB1572338A - Gas discharge lamps

Info

Publication number: GB1572338A
Application number: GB3955578A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1976-10-09
Filing date: 1976-11-02
Publication date: 1980-07-30
Also published as: DE2645794C3; DE2645794B2; DE2645794A1

Description

(54) GAS DISCHARGE LAMPS (71) I, ALFRED WALZ, Am Kurzarm 7, 7830 Emmendingen, Federal Republic of Germany, A German citizen, do hereby declare the invention for which I pray that a patent may be granted to me and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to gas discharge lamps fed by way of rectifiers from an alternating current source, for example flourescent lamps having a double electrode arrangement and discharge-tight cross-connection of the electrode chambers. A double-electrode arrangement with gas discharge-tight cross-connection of the electrode chambers for gas discharge tubes operated with direct current is already known, in which the cross-connection is in the form of an annular gap between a cylindrical tube and a cylinder which is inserted into the tube and is closed at least one end.It is thereby ensured that the two electrode chambers are in communication with one another by way of a channel of adequately small cross-section so that no electric gas discharge can take place in that channel, but a current of metal vapour or gas molecules can pass through this channel as the result of a pressure difference and/or diffusion.

The impoverishment of the anode region which is disadvantageous to the production of light, for example impoverishment in respect of mercury ions, the so-called cataphoresis, can be prevented in the case of direct current operation.

For the formation of a direct current opera ated gas discharge lamp working without cata- phoresis it is also known for the cross-connection between the electrode chambers connected to the electrical ignition and operating direct voltage to be formed by a capillary which extends through a barrier wall which is preferably made of glass and on which the electrodes are brought up from both sides in order to avoid, except for a short distance, discharge-free zones in the region of the capillary.

For the direct current operation of gas discharge lamps from an alternating current source a circuit arrangement is known in which a feed circuit arrangement in the form of a voltage multiplier circuit, composed of rectifier diodes and capacitors, and a lower-power ignition circuit supplying a high voltage are combined to form a voltage multiplier circuit consisting of a plurality of serially connected voltage doubler stages.

An arrangement is also known for feeding gas discharge lamps from an alternating current mains with a rectifier device in the form of a voltage multiplier circuit having a choke coil through which the lamp current flows, the iron core of the choke coil having an internal cavity in which the components of the rectifier device are accommodated.

The problem underlying the invention is that of providing, by utilising the known devices and constructional principles, a gas discharge lamp which gives a light yield greater than that of known fluorescent tubes and which can be easily manufactured by series production methods.

According to the invention there is provided a fluorescent lamp fed by way of a rectifier from an alternating current source, in the form of an elongated substantially rectangular unit, the unit having an electrode chamber produced by shaping a straight piece of tubing tu provide two longer sides of the rectangular unit and one shorter side defined by a U-shaped end portion of the tube integral with the longer sides, a prefabricated connecting device in the form of a tubular member containing a gas-discharge proof barrier element which divides the tubular member, and two electrodes located one on each side of the barrier element, the barrier element being permeable to mercury vapour, the device joining the free ends of the tube to form the other shorter side of the unit.

Through the construction according to the invention a practically doubled discharge path is achieved while the length of the arrangement remains substantially the same. This provides a substantially better ratio between cathode fall and operating voltage. In addition, the crosssection of the tube can be made smaller, so that a higher operating voltage in the region of 300 V can be optimally utilised.

The barrier element is preferably a dia phragm of sintered glass fibres.

It is particularly advantageous for the electrode holders to be joined to cold-start oxide electrodes.

In the component between the free ends it is expedient for at least one pump stem to be provided in the prefabricated conducting device.

In a preferred embodiment of the invention a ballast for ignition and operation for connection to an alternating current mains is disposed in the interior of the rectangular shape defined by the shaped tube in such a manner that the electrode connections supplied with the high direct voltage of the series-connected apparatus are electrically insulated and the pump stem end or ends are covered in such a manner as to be mechanically protected, while only two lowvoltage connections for connection to an alternating current source of the usual mains voltage are brought out.

In a preferred embodiment of the invention it is also possible to provide an "Edison" screw base as the power supply connection means.

The invention also provides a method of making a tube for the lamp wherein a straight tube is first bent into an elongated U-shape, the tube ends, which at first are still straight, free, and open, are each shaped into a quarter-circle so that the free ends face one another, a prefabricated barrier element is fitted into the gap formed by the space between the free ends of the tube and is then joined to the tube ends by glass fusion.

It is particularly advantageous for the straight tube to be coated with fluorescent material before the bending operation.

An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings and in which: Figure 1 illustrates an intermediate stage in the production of a gas discharge lamp in accordance with the invention, Figure 2 shows a component which can be used in conjunction with the bent tube of Figure 1, Figure 3 is an end view of the part shown in Figure 2, and Figure 4 shows a complete gas discharge lamp according to the invention, with an "Edison" screw base.

In the gas discharge lamp shown in Figures 1 to 4, a straight length of tubing, which is drawn by series production methods in known automatic machines and is preferably processed after coating with fluorescent material, is bent in an automatic machine into an elongated Ushape as shown in Figure 1, with desired dimensions, such as tube length and spacing. In conjunction with the same or a subsequent bending operation the tube ends 21, 22, which are at first still straight, free, and open, are each bent into a quarter-circle bend in such a manner that the ends 21 and 22 are opposite one another at a predetermined distance 23. In a further operation a prefabricated anti-cataphoresis component shown in Figures 2 and 3 is fitted into the gap 23 and thereupon joined to the tube ends 21 and 22 by a glass fusion process, preferably with the aid of a special automatic machine.In Figures 2 and 3 the component 25 is shown partly in section and in end view respectively. A gas discharge-proof diaphragm 24, which however is permeable to mercury vapour and which is for example composed of sintered glass fibres, is disposed in a length of glass tubing whose diameter and wall thickness are approximately equal to those of the parts 21 and 22 and whose length corresponds approximately to the distance 23 between the bent tube ends 21 and 22. Two electrodes 26 and 27, which, in this embodiment, are cold-start oxide electrodes which are self-heated by the operating current, are disposed one on each side of the diaphragm 24. In addition, two pump stems 28 and 29, each of which is secured adjacent the end of a respective tube end 21 or 22, are inserted in the glass tube 25.Current supply leads 30 and 31 for the electrodes 26 and 27 are sealed gas-tightly in the glass tube 25. All these components are secured to the tube 25 to form a prefabricated unit which is then joined to the tube ends 21, 22.

Figure 4 shows a completed gas discharge lamp according to the embodiment, in the form of a gas discharge tube 32 mechanically closed on itself to form an elongated U-shape and having a fused-in barrier element 24, a rectifier ballast 18 being disposed in the space between the two longer lengths of tubing, the connection to the mains of this ballast being made by means of a standard Edison base 33 in the example illustrated. In this arrangement the rectifier ballast 18 is preferably in rod-form of circular cross-section and provided with a light-reflecting surface.

In Figure 4 the insulating covering 1 8a is circular and so shaped that the electrode connections are covered in such a manner as to provide electrical insulation against contact, while the pump stems 28, 29 are protected against mechanical damage.

WHAT I CLAIM IS: 1. A fluorescent lamp adapted to be fed by way of a rectifier from an alternating current source, in the form of an elongated substantially rectangular unit, the unit having an electrode chamber produced by shaping a straight piece of tubing to provide two longer sides of the rectangular unit and one shorter side defined by a U-shaped end portion of the tube integral with the longer sides, and a prefabricated connecting device in the form of a tubular member containing a gas-discharge proof barrier element which divides the tubular member, and also two electrodes located one on each side of the barrier element, the barrier element being permeable to mercury vapour, the device joining the free ends of the tube to form the other shorter side of the unit.

2. A lamp according to claim 1 wherein the barrier element is a diaphragm of sintered glass fibres.

3. A lamp according to claim 1 or 2, wherein the electrode holders are connected to coldstart oxide electrodes.

4. A lamp according to any one of claims 1 to 3, wherein at least one pump stem is provided in the prefabricated connecting component.

5. A lamp according to any one of claims 1 to 4, wherein in the interior of the rectangular shape defined by the shaped tube a ballast is provided for ignition and operation for connection to an alternating current source, in such a manner that the electrode connections supplied with the high direct voltage of the ballast are electrically insulated and the pump stem end or ends are covered so as to be mechanically protected and only two low-tension connections for connection to an alternating current source of main voltage are brought out.

6. A lamp according to any one of claims 1 to 5, wherein a pair of contact pins is provided on said other of the shorter sides for connection of the lamp to a power supply.

7. A lamp according to any one of claims 1 to 6, characterised in that an Edison base is provided as the power supply connection means.

8. A method of producing a gas discharge tube for a lamp according to any one of claims 1 to 8, wherein a straight tube is first bent into an elongated U-shape, the tube ends, which at first are still straight, free, and open, are each shaped in a quarter-circle so that the free ends face one another, a prefabricated barrier element is fitted into the gap formed by the space between the free ends of the tube and is then joined to the tube ends by glass fusion.

9. A method according to claim 8, wherein the straight tube is coated with fluorescent material before the bending process.

10. A fluorescent lamp substantially as hereinbefore described and with reference to Figures 1 to 4 of the accompanying drawings.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. against mechanical damage. WHAT I CLAIM IS:

1. A fluorescent lamp adapted to be fed by way of a rectifier from an alternating current source, in the form of an elongated substantially rectangular unit, the unit having an electrode chamber produced by shaping a straight piece of tubing to provide two longer sides of the rectangular unit and one shorter side defined by a U-shaped end portion of the tube integral with the longer sides, and a prefabricated connecting device in the form of a tubular member containing a gas-discharge proof barrier element which divides the tubular member, and also two electrodes located one on each side of the barrier element, the barrier element being permeable to mercury vapour, the device joining the free ends of the tube to form the other shorter side of the unit.