U.S. Philips Corporation

Koninklijke Philips Corporation N.v.

Jean J Heuvelmans

Franciscus A Ligthart

Jan Evert Van Der Werf

Hendricus Franciscus Van Tongeren

Winston Donald Couwenberg

Marco Haverlag

Johannes T Van Kemenade

Andreas S Geven

Hui-Meng Chow

Albert Bouwknegt

Johannes T deHair

Gerardus H Siebers

John Fitzgerald

Abraham L De Smit

Andreas Sebastianus Gertrudis Geven

Johannes W Ter Vrugt

In a lighting arrangement comprising a low-pressure discharge lamp and a high-frequency ballast for cold-igniting and operating the low-pressure discharge lamp, said low-pressure discharge lamp is equipped with electrodes which each comprise two or more double-spiral tungsten electrode bodies covered with an emitter. The switching performance of the low-pressure discharge lamp is very high.

Discharged lamp with multiple electron emissive electrode bodies

At least one of the electrodes (6a) has a coil (60a) of a refractory metal which is electrically connected to current supply conductors (7a, 7a') which extend to outside the discharge vessel. The coil (60a) has a central portion (61a) which is coated with an electron-emitting material and an end portion (62a, 62a) on either side thereof, which end portions are covered with a protecting material which is mainly formed by one or more oxides of calcium and/or magnesium.

Low-pressure discharge lamp with filament having protective coating

A lighting unit according to the invention comprises a supply unit (1) and a low-pressure mercury discharge lamp (2). The low-pressure mercury discharge lamp has a light-transmitting discharge vessel (3) which is provided with a luminescent layer (3) on an inner surface and which encloses in a gastight manner a discharge space (4) which is provided with a filling comprising mercury and one or several rare gases. A first (5a) and a second electrode (5b) are arranged in the discharge space, each comprising a coiling of a metal wire coated with one or several electron-emitting metal oxides. Each electrode is electrically connected to a respective current supply conductor (6a, 6b) which extends to outside the discharge vessel (3). The current supply conductors are electrically connected to the supply unit outside the discharge vessel, the unit ignites the low-pressure mercury discharge lamp in the state upon switching-on. During nominal operation, at least a portion (5a*) of each electrode (5a, 5b) passes an electrode current Iel having an effective value Iel which is at least 1.8 times the minimum electrode current Ip4 required for thermal emission. The lighting unit according to the invention has a long switching life.

Lighting unit, low-pressure mercury discharge lamp, supply unit, and

A low-pressure discharge lamp of the invention is provided with a gas-tight discharge vessel (10) which contains an ionizable filling. Electrodes are arranged inside At least one of the electrodes has a tungsten coil (20.sub.A) which is electrically connected to current supply conductors (30.sub.A, 30.sub.A ') which extend to outside the discharge vessel (10). The coil (20.sub.A) has a central zone (21.sub.A) covered with an electron-emitting material (22.sub.A) and, on either side, boundary zones (23.sub.A, 23.sub.A ') between the central zone (21.sub.A) and respective current supply conductors (30.sub.A, 30.sub.A '). The boundary zones (23.sub.A, 23.sub.A ') having a covering (24.sub.A, 24.sub.A ') of a protective material, comprising a ceramic material having a specific resistance less than 1000 .mu..OMEGA..cm.

Low-pressure discharge lamp

A low-pressure mercury vapour discharge lamp having a tungsten coil electrode which is supported at either end by a respective current supply wire and which has emitter-coated central turns and, on either side thereof, end turns which are free from emitter. Each of the current supply wire ends with adjoining end turns of the coil is surrounded by an electrically insulating sleeve, such as a glass tube, as a result of which the switching life of the lamp is considerably increased.

Low-pressure mercury vapor discharge lamp

A low-pressure mercury vapor discharge lamp with a luminescent layer whose emission mainly lies in three spectral ranges and whose loading amounts to at least 500 W per m.sup.2 surface area of the luminescent layer, is characterized by having an absorption layer of a luminescent aluminate activated by trivalent cerium and having a garnet crystal structure. The absorption layer permits the obtaining of low color temperatures (down to 2000 K.).

Low-pressure mercury vapour discharge lamp

Low-pressure mercury vapor discharge lamp having a curved discharge vessel in which a mercury discharge is maintained between the electrodes and in which furthermore an amlagam is provided to control the mercury vapor pressure, the discharge vessel containing a rare gas mixture which contains at least 50 at.% krypton at a pressure of 130 to 520 Pa.

Low-pressure mercury vapor discharge lamp having a relatively small discharge vessel containing as the buffer gas a rare gas mixture which is rich in helium, but which also comprises a quantity of one or more heavier rare gases, preferably crypton. The heavier rare gases increase the arc voltage.

A device for operating a low-pressure sodium vapor discharge lamp without a ballast. The electrode voltage drop near a main electrode of the sodium lamp is influenced by a change in the pre-heating current of that electrode and/or a change in the effective area of the electrode. The changed electrode voltage drop thus obtained provides a mechanism whereby any changes in the lamp current are opposed so as to produce ballast-free lamp operation.

Arrangement including a gas and/or vapor discharge lamp

The invention relates to a gas and/or vapor discharge lamp which is provided with a discharge tube and an outer bulb which envelops this tube, whilst the heat insulation in the space between the discharge tube and the outer bulb can be changed. According to the invention the heat insulation is changed by means of a reversible hydrogen getter which is located in the space between the outer bulb and the discharge tube. In this way it is obtained that the lamp can either be operated without a stabilizing ballast or that it is less sensitive to variations in the mains supply.

Gas-and/or vapor discharge lamp

A discharge lamp has an electrically conducting transparent layer and a temperature control which responds to variations of the lamp current to control lamp temperature. A control member causes an auxiliary current to flow intermittently through the said layer. The temperature control is adjusted so that in the operational condition the lamp will always be operating in a voltage-current range having a positive nature. As a result, the lamp does not require an electric stabilizing ballast.

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Eindhoven, Netherlands

Jean J Heuvelmans